UNIT 1

INTRODUCTION

1.1 IMPORTANCE OF MAINTENANCE

 Maintenance is the routine repairing work, required to keep the vehicle in good condition so
that it can be utilized for designed capacity and efficiency.
 Repair is the restoration of the vehicle to a condition substantially equal to its original
condition by changing Parts (or) by reconditioning it.

Objectives of maintenance system

 To keep the vehicle available for protective work for maximum period.
 To extract optimum life for the vehicle.
 To get maximum utilization of vehicle at minimum cost.

1.2 PREVENTIVE (SCHEDULED) AND BREAK DOWN (UNSCHEDULED)

MAINTENANCE

 Scheduled maintenance system:-

In this system, servicing of the vehicle is done at pre determined time interval, in order to avoid
breakdown of the vehicle

 Un Scheduled maintenance:-

In this system, servicing or repairing work is done only after the vehicle breakdown.

 Advantages of scheduled maintenance:

It reduces cost of operation it renders work scheduling easy. It reduces starting problem. Control of
store inventory easy

1.3 NEED FOR MAINTENANCE

For proper vehicle maintenance, inspect the following:

 OIL AND COOLANT LEVELS.

 AIR FILTER.
 TIRE PRESSURE AND TREAD DEPTH.
 HEADLIGHTS, TURN SIGNALS, BRAKE, AND PARKING LIGHTS.
 OIL & FILTER.
 ROTATE TIRES.
 WAX VEHICLE.
 TRANSMISSION FLUID.

1.4 Why is it important to maintain the condition of your vehicle?

Properly maintaining your vehicle will not only ensure its safety and dependability, but
may also increase fuel efficiency as well as help maintain your vehicle's value. It is
recommended to consult your vehicle's owner’s manual and follow its preventive vehicle
maintenance schedule.

1.5 What is the classification of maintenance?

Five types of maintenance are in fact recurrent in the industry: corrective, preventive,
condition-based, predictive and predetermined

1.6 What is vehicle diagnosis?

A car diagnostic test is a digital analysis of your car's various computer systems and
components. Modern vehicles are much more digitized than people may be aware of Specialized
software works whenever your car’s engine is powered on to monitor various features and create
data reports that can then be collected and analyzed during a car diagnostic test.
1.7 What Parts of a Car Are Tested?

These days, car diagnostic tests analyze various aspects of your vehicle. Specifically, they check for:

 Problems with your car’s engine or individual components

 Issues with your car’s transmission and responsiveness
 Problems with brake responsiveness
 Potential contamination or faults with your car’s exhaust system
 Signs of wear and tear or breakage with major components, such as the fuel injector, ignition
coils, and throttle

Though these results can help drivers assess their vehicle’s state, keep in mind that car diagnostic
tests are not perfectly accurate. They cannot tell the technician or tester precisely what the problem
is in many cases. Instead, they’re used to narrow down the location of an issue or potential error so
that mechanics can more quickly identify and take care of a problem for drivers.

1.8 Benefits of Car Diagnostic Tests

Car diagnostic tests are valuable for a variety of reasons.

 Car diagnostic tests help you detect errors before they become catastrophic, saving you money
in the long run.
 Furthermore, catching errors before they become more serious could potentially save your life
or the lives of others. Car diagnostic tests can, for instance, tell you when you need to replace
your brakes before they fail on the freeway.
 Car diagnostic tests can also check your car’s onboard computer system for any manufacturer
notifications or stored information. The data can help technicians provide the best repairs
possible for your vehicle.

1.9 What is maintenance battery?

Figure 1.1battery

 As the name might suggest, Maintainable batteries have removable caps which enable you
to visually check the electrolyte level in each cell. The lifespan of the battery can be
extended by periodically checking the electrolyte level, and top up with demineralised water if
required.
1.9.1Why is battery maintenance important?

 The buildup can cause a small discharge and weaken the battery. It is a good idea to fully
remove the battery so that the tray can also be cleaned up. At times, the battery connections
will get dirty or corroded. When this happens, it is time to clean them up.

1.10 What is tyre maintenance?

 Inspection and maintenance of tires is about inspecting for wear and damage on tires so that
adjustments or measures can be made to take better care of the tires so that they last longer, or
to detect or predict if repairs or replacement of the tires becomes necessary.

1.10.1What is the importance of maintaining tyres?

Proper inflation pressure is important for safety and fuel economy. If your tyres are under
or over inflated, it can increase fuel consumption and make them more susceptible to wear and tear.
Having the wrong pressure can also result in a blowout, which can cause you to lose control of your
car

1.10.2 What is the single most important maintenance function of a tire?

Maintaining proper inflation pressure is the single most important thing you can do to help your
tires last longer and stay durable. Under inflation is the leading cause of irrepairable tire damage and
may result in severe cracking and subsequent air loss

1.11 The Basics of Vehicle Safety Maintenance

No matter how well you drive, you are not safe unless your vehicle is in good condition. You keep
your vehicle in good condition by having the vehicle properly maintained. If it is not, your car could
fail you at a critical moment, and you could be in a serious crash. Read your automobile owner's
manual carefully to become familiar with your vehicle's maintenance schedule and requirements.
Maintenance regimes vary widely from one vehicle to another.

1.12 What parts of the vehicle should be properly maintained?

Virtually all of your vehicle's mechanical systems can affect fuel efficiency if not properly
maintained. Follow the manufacturer's recommendations for checking the engine, cooling and
ignition system, brakes, drive train and emission-control system. You should consider your vehicle
from front to back, bottom to top.

 Lights

Make sure that all of your lights work and that your light lenses are clean. Check headlights,
taillights, directional signals, and interior lights.
  Windshield

Windshields are made out of laminated safety glass which reduces transmission of high frequency
sound and blocks 97 percent of ultraviolet radiation. A thin layer of flexible clear plastic film (PVB)
is sandwiched between two or more pieces of glass. This plastic film serves to hold the glass in
place. If the glass breaks, the film helps lessen injuries which could be caused by flying glass. This
structure also affords protection for those inside the vehicle by obstructing possible projectiles from
entering the vehicle through the windshield.

If your vehicle has tinted windows, check with your local law enforcement agency to make sure it is
in compliance with state sunshading specifications.

It may surprise you to know that the first windshield wipers invented were operated manually. The
driver had to physically move a lever back and forth inside the car. Today, of course, windshield
wipers work electrically. Some vehicles (especially SUV types) have windshield wipers on the rear
window as well. Some vehicles even have windshield wipers on the headlights.

Wiper blades work like squeegees. A thin rubber strip is attached to the blade arm which is swept
across the windshield to wipe away the water. A rubber on new blades is clean and smooth so that
water can be wiped away. As blades age and become worn, the seal against the window lessens due
to nicks or cracks in the rubber or from becoming brittle with age. Worn blades can leave streaks on
the windshield that interferes with driver visibility. It is important to clean wiper blades to remove
any dirt buildup. Your vehicle's windshield washer system will help keep the windshield and the
wipers clean. Wiping the rubber edge with window cleaner until clean may prolong the blade's life.
When you notice any change in visibility due to the wiper's performance, replace them with new.

It is important to keep your windshield clean on the inside as well as on the outside. Dirt builds up
on the inside that can affect visibility as well.

 Mirrors

All vehicles should be equipped with one rearview mirror mounted inside the vehicle that allows a
view to the rear of at least 200 feet. A rearview mirror should also be placed on each side of the
vehicle mounted on the outside of the vehicle's front doorframes. Make sure that your mirrors are
clean and pointed in the correct direction. The mirrors are designed to assist drivers in keeping track
of traffic around their vehicles.

 Tires

Tires are designed to grip the road and give the driver directional control. Bald, excessively worn, or
improperly inflated tires decrease the ability of the driver to control the vehicle. Rotating your tires
helps prolong their life and improve fuel economy. On most vehicles, tires should be rotated about
twice a year; however, you should consult your owner's manual for the recommended rotation
pattern and frequency for your vehicle.
Rolling resistance is a key factor that affects a vehicle's fuel efficiency. Make sure that your tires are
properly inflated and not worn away. The best way to reduce rolling resistance is to maintain correct
tire pressure. Rolling resistance results in premature tread wear when your tires are under-inflated,
increasing fuel consumption. Operating a vehicle with just one tire under-inflated by 6 pounds per
square inch (PSI) can substantially reduce the life of the tire and increase the vehicle's fuel
consumption by three percent. Tire pressure needs special attention in cold weather. It can be
expected to drop by about 1 PSI for every 10oC drop in temperature. Tires also lose a certain
amount of pressure due to their permeability (by some estimates, as much as 2 PSI per month). Tire
pressure should be checked when the tires are cold (for instance, when the vehicle has been
stationary for at least three hours).

Wheel alignment should be checked once a year. Misaligned tires will drag and will not roll freely
as they are intended to do. This will increase fuel consumption, reduce tire life, and cause problems
with the vehicle's handling and ride. While driving, you can perform a self-check on your wheel
alignment. On a straight, flat and traffic-free stretch of road, rest your hands lightly on the steering
wheel and drive at an even speed. If the vehicle pulls to one side, the wheels may be misaligned.

Wheels should also be balanced. If they are out of balance, the driver will feel a pounding or shaking
through the steering wheel. This pounding will shorten the life of other suspension components and
will produce uneven tire wear, which will increase fuel consumption. Tires that are not balanced
exhibit a wear pattern that looks like a series of bald spots.

Remember, don't neglect the spare tire. Make sure the necessary tools for replacing a tire are
appropriately accessible.

You should check tire pressure and look for signs of uneven wear or embedded objects that can
cause air leaks. In winter, check tire pressure whenever there is a sharp change in temperature.

 Oil

Car engines run particularly well when they are regularly lubricated. Oil lubricates the moving parts
of the engine, minimizing metal-to-metal contact, thereby reducing friction and carrying away
excess heat. Oil also captures dirt, metal shavings and other impurities from the engine enabling the
transfer of these injurious substances into the vehicle's oil filter. For best engine performance, fuel
efficiency and reduced emissions, use only the oil recommended in your vehicle's owner's manual.
Regular engine oil changes cost between $10 and $30 — a far cry from the expense of replacing or
rebuilding an engine!

Check around the car and under the engine for fluid leaks. Generally, you can often identify the type
of fluid that is leaking by its colour. Oil is black, coolant is a bright greenish yellow, automatic
transmission fluid is pink, and power steering and brake fluids are clear, with a slight brown tinge.
All of these fluids are oily to the touch.
  Belts, hoses, regular tune-ups

Have your belts and hoses checked at the regularly scheduled time periods mentioned in your
owner's manual. Also, get a tune-up at the scheduled maintenance time. Check under the hood for
cracked or split spark plug wires, cracked radiator hoses or loose clamps and corrosion around the
battery terminals.

 Emission-control systems

Modern vehicles are equipped to treat exhaust emissions before they are released into the
atmosphere. The emission-control system must be inspected and maintained according to the
manufacturer's recommendations. If you experience problems such as stalling or poor acceleration,
or if your exhaust produces black or blue smoke, your vehicle is probably polluting the air and needs
servicing.

 Ignition systems

Proper maintenance of your vehicle's ignition system is critical. Spark plugs ignite the air-fuel
mixture. If one or more of the plugs is worn or malfunctioning, the engine will misfire, and some
fuel will remain unburned. Worn or damaged spark plug wires can also cause misfiring. A misfiring
engine wastes fuel, produces higher levels of emissions and generally performs poorly.

 Brakes

The foot brake must be capable of stopping the vehicle within a distance of 25 feet at a speed of 20
miles per hour. The parking brake should be adequate to stop and hold the vehicle. While driving,
you can perform a self-check on your brake system. On a straight, flat and traffic-free stretch of
road, rest your hands lightly on the steering wheel and apply the brakes gradually. If the vehicle
swerves to one side, one of the brake linings may be worn more than the other, or the brakes may
need adjustment. If this happens, make sure to get the vehicle to a proper mechanic.

Your vehicle's brake pedal is designed so that when it is pressed, the force of the pressure is
multiplied several times. The hydraulic system that operates your vehicle braking system transmits
the force from your foot to its brakes through brake fluid.

It is important to pay attention to any strange sounds you may hear when you apply your brakes,
such as grinding or squeaking sounds. Any such noise should alert you to have your brakes
inspected. The brake pad wear limit indicators on disc brakes give a warning noise when the brake
pads are worn to where replacement is required.

Your vehicle's owners manual will supply you with the correct information on maintaining the
correct level and type of brake fluid.
1.13 Why should I bother to do vehicle maintenance?

Maintenance requirements vary widely from one vehicle to another. Failing to follow your particular
vehicle owner's manual's maintenance regime could void your vehicle's warranty. To keep the
manufacturer's warranty valid (not to mention ensuring maximum fuel economy), your vehicle must
be maintained to the standards recommended in the owner's manual.

It's simple — your vehicle will last longer and work better. The time to find out that your car has a
problem is in your driveway, not out on the roadway. Additionally, a properly maintained vehicle is
a safer vehicle. Through proper maintenance, your vehicle will function as advertised and will
increase the potential for you to come through an emergency situation in one piece.

1.14 SCHEDULED AND UNSCHEDULED MAINTENANCE

 Scheduled Maintenance

In this system, servicing of the vehicle is done at pre-determined time interval, in order to avoid
breakdown of the vehicle, this type of maintenance is also called as preventive, periodic and
operative maintenance

 Maintenance scheduled for car

 Wash and lubricate chassis, do not spray under chassis
 Drain drum, gear box and axle, flush and refill with proper lubricants.
 Check under chassis for evidence of water, oil, brake fluid, shock absorber and
petrol leaks
 Tighten engine, steering joints, U bolts and chassis bolts to torque specifications.
 Lubricate rear axle bearing. Tighten rear axle shaft nuts to torque specification.
 Check operation of body hardware, doors, glasses, locks and keys
 Check and fill battery, clean and tighten terminals
 Check operation of all instruments, lights horns and accessories
 Check and adjust fan belt tension
 Check clutch pedal free travel and linkage
 Adjust brakes. Check and adjust pedal free travel.
 Check master cylinder fluids
 Check wheel alignment
 Aim headlights
 Tune engine, including adjustment tappets
 Adjust ignition timing and carburetor
 Clean body rim and tires
 Carry out daily and weekly maintenance
UN scheduled maintenance

In this system, servicing or repairing work is done only after the vehicle brakedown. This type of
maintenance is also called as breakdown maintenance.

Placing an emergency vehicle out of service

1. Braking system

 Air line leak or bulge

 Loose compreeor mounding bolts
 Evidence of oil seepage
 Cracked brake drum

Inoperative low air warning device

 Master cylinder leakage

2. Steering system
 Excessive free play
 Worn or faulty universal joints
 Steering wheel not properly secured
 Loose tire rod ends
 Any conditions that interferes with free movements
3. Exhaust system
 Exhaust leak forward or below the gas
4. Frame
 Cracked loose, or broken frame member
5. Fuel system
 Visible fuel leak
 Fuel tank not securely attached
6. Spring and suspension
 Cracked, loose or missing U bolt or other spring to axle clamp
 Any broken main leaf in the leaf spring
 Any displaced leaf that could result in contact with tire
 Broken or missing shocks
 Missing or broken axle bolts
7. Windshield / Wipers
 Visuals cracks or distortion that impair or inoperative
 Both brake lights missing or inoperative
 Both tail lights missing or inoperative
 Any turn signal missing or inoperative
 Inoperative siren
 Emergency lighting not visible from all sides
8. Drive train
  Engine overheating
 Motor oil in engine
 Engine coolant in motor oil
9. Broken or missing fan belts
 Coolant leak at water pump
 Any major coolant leak
 Automatic transmission overheating
 Defective clutch components
 Defective foot throttle
 Defective charging system
10. Cab / Body components
 Missing or broken mirrors that obstruct or limit the driver view
 Defective door latches

1.15CLASSIFICATION OF MAINTENANCE
1.16 VEHICLE INSURANCE

Vehicle insurance (also known as car insurance, motor

insurance or auto insurance) is insurance for cars, trucks, motorcycles, and
other road vehicles. Its primary use is to provide financial protection against
physical damage or bodily injury resulting from traffic collisions and against
liability that could also arise there from. Vehicle insurance may additionally offer
financial protection against as theft of the vehicle, and against damage to the
vehicle sustained from events other than traffic collisions, such as keying and
damage sustained by colliding with stationary objects. The specific terms of
vehicle insurance vary with legal regulations in each region.
 Automotive service procedure.

Check Service Log Book for history & other work due
Check if vehicle is registered, so it can be test driven legally
Check to see how many KM since last oil change
If over 7,000km recommend engine flush to Service Adviser
Test drive vehicle and report
Carry out Safe T Stop test, dynamically testing steering, suspension and brakes
Checks for lights, wiper, washer and horn (report)
Check cooling system hoses (report)
Check and test brake fluid (report)
Check air filter and clean if not replaced (report)
Check radiator condition (report)
Test coolant / inhibitor condition with test strips (report)
Connect cooling system pressure tester
Check power steering fluid level and condition (report)
Check automatic transmission level and condition (report)
Visual check over the whole engine bay (report)
Audible check for anything unusual (report)
Check accessory belts with testers, check tensioner and tensions (report)
Test battery, alternator output, print report, attach to job card ü
Disconnect pressure tester (report)
Raise vehicle and drain engine oil ü Perform 65 point check under
vehicle (report)
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 Check all diff levels, Transfer case levels and Gearbox levels
Grease all grease nipples, look for blanking plugs where grease nipple need
to be fitted (report) Grease steering stops
Measure brake pad wear, remove wheels if needed (report)
Drum brakes, remove drums wipe down shoes, check brake wheel
cylinders for leaks ‘pulling back rubbers’ & (report)
Measure tyre tread depth (report)
Check flexible brake hoses for cracks (report)
Check shock absorbers for leaks (report) ü Check oil leaks (report)
Check all mounts and rubbers (report) ü Remove oil filter if accessible
under vehicle and fit new filter Adjust brakes and it wheels
Check tyre pressures
Fit sump plug & clean around oil filter area and sump plug area
Fill engine oil, start engine and recheck ü Wipe down under bonnet
Fill out new service sticker
Clean off old service sticker & residue & fit new service sticker
Lube door strikers
Wash and chammy vehicle & apply tyre shine
Test drive ü Park vehicle & give keys to Service adviser to check.
1.17 MOTOR VEHICLE WORKSHOP OPERATION

A motor vehicle workshop operation consists of operating a workshop on a

commercial basis involving any of the following relating to motor vehicles:

 Maintaining mechanical components, engine cooling radiators or

body panels; • Spray painting body panels; or
 Detailing or washing. A motor vehicle workshop for the purposes of
this legislation does not include:
 Operating a workshop for the purposes of a farming, gas, mining or
petroleum activity
 A fleet vehicle workshop to maintain or repair fewer than 10 vehicles; Washing
motor vehicles if all the water used is discharged to a sewerage infrastructure
under a trade waste approval or the washing is required under a law of the State
for weed or pest control;
 Operating a workshop to maintain or repair:- – auto electrical, exhaust,
suspension or air conditioning components of motor vehicles; or – wheels or
tyres of motor vehicles, including wheel alignments; or – minor scratches,chips
or dents using a brush, air brush or paint less method; or – motor vehicle hoses.
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  operating a mobile and temporary workshop

1.18 SAFETY RULES FOR AUTOMOTIVE MAINTENANCE

Eye protection is mandatory for all operations which produce sparks, chips,
flying objects or involve use of corrosive chemicals. Face shields shall be
worn for all operations that involve use of a high-pressure steam system.
Appropriate gloves and protective clothing shall also be worn.
Mechanics shall not wear loose clothing around rotating equipment. Clothes
saturated with oil, grease, or solvents shall not be worn.
Compressed air shall not be used to clean clothing.
Shop floors will be kept free of grease, oil, gasoline, or other slipping hazards.
Employees shall not use defective electrical or mechanical shop equipment
or hand tools. All automotive shop machinery shall be grounded.
Vehicles shall not be towed unless appropriate tow bars or other approved
equipment is used.
Jacks, hoists, or other lifting devices shall not be used beyond the safe load
capacity recommended by the manufacturer. Employees shall not remain in
vehicles being lifted by hydraulic lifts or jacks.
Mechanics shall not work under vehicles that are not properly supported
with approved stands. Makeshift stands made of wood, cement blocks, or
boxes shall not be used.
Gasoline, acetone, kerosene, or similar solvents shall not be used to clean
hands, floors, walls, or other surfaces. Parts shall be cleaned only in
approved containers using appropriate solvents.
Employees shall not use standard sanitary sewer drains for the disposal of
gasoline, oil, or solvents. Contact EH&S for disposal guidelines.
Tanks or containers that are used for gasoline or other flammable solvents
shall not be mechanically opened or repaired by welding without purging
and cleaning.
Do not begin tire inflation before the rim is properly seated. It is dangerous
to attempt adjustment with a hammer when the tire is being inflated.
Do not place hands or arms between mounted dual tires during inflation.
Always use a long air chuck for inflation.
Do not change tires on the road unless wheel chocks and warning devices
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 are used. Flares should be used to warn others whenever a vehicle tire is
changed while on a heavily used road.
Changing of tires on split-rim wheels will be performed only by individuals
with proper training and using only appropriate equipment.

1.19AFETY EQUIPMENT’S

Service technicians help ensure that each vehicle has the following safety equipment:

Portable Fire Extinguishers – proper type, size, and rating

Emergency Reflective Triangles – warning devices for stopped vehicles
Wheel Chocks – prevent accidental movement of vehicle while parked
First Aid Kits – to match the maximum capacity of persons per vehicle

The US Department of Transportation and the Federal Motor Carrier Safety

Administration (FMCSA), regulate the safety of commercial motor vehicles used
on highways for transporting passengers or property.

FMCSA regulation 49 CFR Part 393.95 requires safety equipment on all of the
following trucks, truck tractors, and buses:

Vehicles with GVWR, GCWR, or gross vehicle weight over 10,000 lb

Buses for compensation with over 8 persons and non-compensation buses

with over 15 Vehicles transporting hazardous material requiring placards

 FIRE EXTINGUISHERS

All buses, trucks, and tractors require a portable fire extinguishers for compliance
with FMCSA. A 10-B:C unit is required for vehicles with hazardous materials and
5-B:C for all others. An extinguishing agent that doesn’t freeze is required, and
each unit must be secured in a manner that prevents sliding, rolling, and vertical
movement. Most installations include a extinguisher in a vehicle bracket..

 EMERGENCY REFLECTIVE TRIANGLES

The FMCSA requires warning devices for stopped vehicles. Although flares are
acceptable, the following equipment is most commonly carried on each vehicle, a a
minimum, for compliance:
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At least 3 bidirectional emergency reflective triangles (P/N TKB1) WHEEL CHOCKS
Wheel chocks (P/N HDLWC) are typically carried on all commercial motor vehicles to
prevent accidental movement while vehicles are parked and during loading and unloading.
Chocks are used against the rear tires in the direction of grade. On even surfaces, chocks
are placed on both sides of tires. Chocks should always be used in pairs.
 FIRST AID KITS
Be sure to check existing first aid kits for proper contents and replace depleted kits after
getting the owner’s consent. Every commercial motor vehicle should carry a complement
of the right safety equipment. Others will appreciate your knowledge of the federal safety
requirements and your recommendations for products and equipment that will help ensure
the safety of vehicles, passengers, and drivers.

1.20 SERVICE INTERVAL

A maintenance service interval is the length of time between vehicle services and inspections.
Maintenance intervals are often based on number of days, odometer readings, or operated engine
hours.

 On-board diagnostics (OBD)

On-board diagnostics (OBD) is a term referring to a vehicle's self-diagnostic and reporting

capability. OBD systems give the vehicle owner or repair technician access to the status of the
various vehicle sub-systems.

1.21 COMPUTERIZED ENGINE ANALYZER STUDY AND PRACTICE

What Is a Computerized Engine Analysis?

When you take your car in for a computerized engine analysis, our expert mechanic will hook the
vehicle's control computer up to a high-tech diagnostic system. A network of sensors and switches
convert and monitor engine operating conditions into electrical signals. The diagnostic system will
send commands to specific systems in your car's engine, including the ignition, emission control,
and fuel systems. If there is a problem with any of the systems, we will check whatever command is
prompted. Once we have identified the source, we can repair or replace components, clear fault
codes, and test drives the vehicle to confirm the system is operating properly. Computerized engine
analysis is the most effective way of diagnosing mechanical problems early on to help you avoid the
hassle of major repairs.

 How Do I Know if My Car Need a Computerized Engine Analysis?

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  Indicator lights display on the dashboard
 Unusual noises
 Poor vehicle handling
 Fluid leaks
 Excessive exhaust smoke
 Stalling

1.22 OBD

What is OBD in vehicles?

OBD is the standard protocol used across most light-duty vehicles to retrieve vehicle diagnostic
information. Information is generated by engine control units (ECUs or engine control modules)
within a vehicle. They are like the vehicle's brain or computers.

1.23 SCANTOOLS

DTC codes are read by a diagnostic tool, such as an OBD 2 scanner, which is plugged into the
vehicle's diagnostic port. The tool communicates with the vehicle's onboard computer and retrieves
the DTC codes. The codes are then interpreted by the mechanic or technician to determine the
specific problem with the vehicle.

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 UNIT – II

POWERTRAIN MAINTENANCE

2.1 EXHAUST GAS EMISSION TESTING

Exhaust gas emission testing is a process where test equipment is used to measure the gases
produced by a car’s engine. A probe is placed in the tailpipe of the car and the exhaust gases are
measured following a strict procedure.

2.2 What is the purpose of an exhaust emission system?

Your vehicle’s exhaust system is designed to take care of toxic emissions your car produces.

It will

1) Direct harmful hydrocarbons away from the driver and passengers, and

2) Reduce the air pollution your car releases into the environment, helping keep the air clean.

An additional benefit is that the exhaust system significantly reduces the amount of noise your car
makers. An exhaust system in working order will keep your car sounding pleasant as it runs and will
reduce noxious gases.

2.3 Where is my car’s exhaust system?

The part of the exhaust system you can easily see is the exhaust pipe under the back of your car, but
the entire system is actually much larger and more involved than that. The entire exhaust system
runs from just behind the engine and along the underside of your vehicle, ending with the tailpipe.

2.4 How does an exhaust system work?

1. As your car emits fumes, the exhaust manifolds—the part of the system connected directly to
the engine—harness the gases into the system.
2. At this point, your car’s catalytic converter takes charge. It takes the gases in the system,
analyzes them, and transforms them into matter that is either less harmful or not harmful at
all.
3. This is a noisy process. Your vehicle’s muffler is what helps keep it quiet.
4. What’s left of the gases exits your car through the tailpipe.

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2.5 How will I know if my exhaust system needs a repair?

One of the first things people notice when their exhaust system is malfunctioning is the amount of
noise their cars make. Your car will begin to sound much more unpleasant if the muffler is out of
order. Another sign has to stop by the gas station more often, as the exhaust system affects your
car’s air-fuel mixture. Additionally, your car’s check engine light might come on. Once you notice
one of these signs, get to a repair shop as soon as you can. Waiting to fix this can damage your car
and will result in a more expensive repair.

Sometimes, though, problems with your exhaust system may go unnoticed without a professional
inspection. For this reason and others, it’s a good idea to have a mechanic inspect your vehicle at
least once per year.

2.6 Exhaust gas temperature

Exhaust gas temperature (EGT) is important to the functioning of the catalytic converter of an
internal combustion engine. It may be measured by an exhaust gas temperature gauge. EGT is also a
measure of engine health in gas-turbine engines

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2.7 ELECTRONIC FUEL INJECTION

2.7.1 What is EFI?

Electronic fuel injection replaces the need for a carburetor that mixes air and fuel. EFI
does exactly what it sounds like. It injects fuel directly into an engine’s manifold or cylinder
using electronic controls. While the auto industry has been enjoying the technology for
decades, it’s not as common in smaller engines

25
2.7.2 What are the Advantages of EFI?
1. Easier Starting
How many times do you go to start your generator by adjusting the choke first?You
won’t have to worry about that with electronic fuel injection. It works for both hot and
cold starting, eliminating one of the major headaches of using small engines.

2. Automatic Altitude Adjustments

As you move from the 100′ elevations here in Central Florida to the mile+ elevations in the
Rockies, you need to adjust the fuel/air mixture to keep an engine running well. EFI does that
automatically through its electronic controls.

3. More Consistent Power

Thanks to the electronic controls that EFI offers, your generator engine is constantly
running at its most advantageous throttle and air mixture settings. With the electronics doing
the work, you never have to wonder if you have everything set just right. You’ll be getting
consistent power and peak horsepower levels where they should be without any guesswork.

4. Better Fuel Efficiency

26
 Electronic fuel injection improves your engine’s fuel efficiency. It’s not uncommon to see
claims of 25% improvement here. That’s good on two levels. First, you’re spending less
money on gas – a big deal for Pros that rely on a generator day in and day out.
The second benefit is that you’ll have to refill the tank less frequently when you’re asking
your generator for more watts. This might only save you a trip or two during the day, but
you’ll appreciate the reduction in productivity interruption.
5. Fewer Emissions

Since EFI engines deliver air and fuel with better accuracy than a carburetor engine,
they generally produce fewer emissions to go along with the improvement in fuel efficiency.
Atomization of fuel also helps burn the fuel more completely.

6. Less Maintenance

Question – what’s the most common maintenance you’re performing on your generator?

If you’re an occasional user, chances are your generator ends up in the shop for a carburetor cleaning
or replacement more than anything else. For Pros that rely on a generator more frequently, it’s likely
oil changes, spark plug changes, and filter cleanings (all of which are easy to do yourself). No matter
which boat you’re in, there’s no carburetor to maintain.

EFI does a better job of avoiding fuel gum up as well. Since the injection process atomizes the fuel,
it burns more completely without leaving behind the residual fuel that a carburetor does.

2.7 What are the Downsides of EFI?

The main difference you’ll notice out of the gate is that EFI is a more costly system than a carbed
(carbureted) engine. If your budget allows you a choice between the two, the advantages are worth it
in my book.

Looking further down the road, there are potentially higher repair costs. Electronic fuel injection is a
more complex system. When something goes wrong with it, it’s likely going to be a more expensive
repair.

27
2.8 WHAT IS THE ENGINE MANAGEMENT SYSTEM?

The engine management system is the arrangement of the devices for controlling a vehicle's
engine. If the car is stolen, the unit will block the vehicle's engine management system and prevent
the engine being restarted. The engine management system shuts down four of the eight cylinders
when the power isn't needed.

2.9 WHAT ARE THE TYPES OF ENGINE MANAGEMENT SYSTEM?

❖ ELECTRONIC FUEL CONTROL SYSTEM

 Mass air flow sensor (MAF) Fuel injectors (FI)

 Ignition systems (IGN) Exhaust gas oxygen sensor (EGO)
 Engine coolant sensor (ECS) Engine position sensor (EPS)

2.10 WHAT ARE THE 5 SENSORS IN THE ENGINE MANAGEMENT SYSTEM?

The most commonly sought-after engine management sensors include air mass meters, knock
sensors, lambda sensors and ignition coils, but you can also find high quality wheel speed sensors,
crankshaft sensors, vacuum sensors and yaw sensors should you require them.

2.11 What are the 8 main engine systems?

28
  Main Engine Systems

 Lubricating Oil System. ...

 Main Bearing Oil System. ...
 Crosshead Bearing Oil System. ...
 Cylinder Lubrication System. ...
 Cooling Water System. ...
 Cooling Water System Description. ...
 Fuel Oil System. ...
 Circulation System.

2.12 TOP 10 ELEMENTS IN A SUCCESSFULENVIRONMENTAL MANAGEMENT

SYSTEM

 For maximum environmental and economic benefits from an environmental

management system and
 To help comply with the EMS requirement under the Toxics Use & Hazardous Waste
Reduction law,
 A business should include the following 10 elements in its system. These elements can
apply to many
 Different EMS models, including ISO 14001. Use this checklist to be sure your system
includes all 10 and keep it on site.

1. Environmental Policy

Reflects how the organization feels about the environment

Identifies environmental impacts of processes and products

Ensures compliance with environmental requirements

Commits organization to prevent pollution, reduce environmental risks and share information
with externalstakeholders

2. Environmental Requirements and Voluntary Initiatives

Employees understand their roles in meeting environmental requirements

Identify management and manufacturing practices that affect the organization's ability to meet
requirements

Identify and work with programs that encourage preventing pollution

3. Objectives/Targets
29
Set the following environmental objectives: comply with environmental requirements;
continuous

Improvement in regulated and non-regulated areas; prevent pollution

Make objectives specific to the organization

Set timeframes to meet objectives

Update objectives as environmental requirements evolve

4. Structure, Responsibility and Resources

Ensure the organization has the personnel and resources needed to meet objectives

Make managers responsible for the environmental performance of their unit

Develop procedures for attaining objectives

5. Operational Control

Establish a procedure to ensure the proper waste management hierarchy is followed

Develop simple procedures to measure and report environmental impacts of processes and
products

6. Corrective and Preventive Action and Emergency Procedures

Document procedures for identifying, correcting and preventing mistakes

Develop emergency procedures to minimize or eliminate adverse environmental impacts

associated withaccidents or emergenciesOregon Department of Environmental Quality
ToxicsUse & Hazardous Waste Reduction6/201711-LQ-016Correct causes of potential
hazards to prevent pollution.

7. Training, Awareness and Competence

Train staff whose roles affect meeting objectives, and make certain staff are capable of
carrying out required duties.

Mandatory trainings include detailed pollution prevention methods.

8. Organizational Decision-making and Planning

30
 Use life-cycle analysis to identify the impact products make on the environment

Empower all employees to make pollution prevention improvements that do not require
significant resources

9. Document Control

For future evaluation, document steps taken to meet objectives

Use electronic documentation to improve record management

Document all pollution prevention suggestions

10. Continuous Evaluation and Improvement

Conduct and document periodic objective-based audits of the organization's performance. Use
audits to assess pollution prevention efforts.

2.13 WHAT IS FAULT DIAGNOSIS IN A CAR?

The “Check Engine” light, also known as the MIL (Malfunction Indicator Light), provides an early
warning of malfunctions to the vehicle owner. There are two types of OBD systems that are used in
vehicles to diagnose faults. OBD-I and OBD-II are two examples.

2.14 WHAT IS FAULT DIAGNOSIS PROCESS?

Fault diagnosis is the process of tracing a fault by means of its symptoms, applying knowledge, and
analyzing test results.

2.15 WHAT ARE THE DIFFERENT TYPES OF FAULT DIAGNOSIS?

Fault diagnosis methods are broadly classified into three main categories: model-based, hardware-
based and history-based

2.16 WHAT ARE THE 4 STEPS TO DIAGNOSIS?

Making a diagnosis involves multiple steps including taking a medical history, performing a
physical exam, obtaining diagnostic tests, and then examining the data to come to the best
explanation for the illness. Taking a medical history is the first step in making a diagnosis.

2.17 WHAT IS THE DIFFERENCE BETWEEN FAULT DIAGNOSIS AND FAULT

DETECTION?

31
Fault detection is based on signal and process mathematical models, while fault diagnosis is focused
on systems theory and process modelling.

2.18 What is OBD 3?

OBD III has been proposed to report emission failures to a regulatory agency, which requires the
owner to have the vehicle serviced before the inspection due date. Very controversial, OBD III is
seen as an invasion of privacy and as of 2021 has not been implemented.

2.19 IDENTIFYING DTC

A DTC, short for Diagnostic Trouble Code, is a code used to diagnose malfunctions in a vehicle or
heavy equipment. While the malfunction indicator lamp (MIL)—also known as the check engine
light—simply alerts drivers that there is an issue, a DTC identifies what and where the issue is.

2.20 Battery Maintenance

The maintenance of an auto battery involves periodic checking of the battery to ensure that your car
runs smoothly. Keep in mind the following for a longer hassle-free battery life:

 CHECK CLAMP

Make sure that the battery is firmly secured to the cradle and the cable clamps and lead wire contact
is proper.

 Avoid grease

Keep the battery top clean and dry. Apply either petroleum jelly or vaseline to cable clamps and
terminals for proper lubrication. Never apply grease.

 Use distilled water

Top up only with distilled water and maintain the level to the line that indicates, maximum. Never
add acid.

 Close tightly

Keep the vent plugs closed tightly.

 Check vent

Ensure that the vent hose in the battery is not folded or damaged by the exhaust system.

 Check regularly
32
Be sure to inspect your vehicle's electrical system regularly, especially the regulator voltage setting.

 Service regularly

Get your battery serviced regularly from your nearest authorised exide dealer.

2.21 What Five Steps Are Done During Battery Maintenance?

1. Charge the Battery. A correct way of charging exists when it comes to forklift batteries. ...
2. Maintain Fluid Levels. The life of a forklift battery relies on optimum water levels to work at
maximum capacity. ...
3. Equalize the Battery. ...
4. Regulate Battery Temperature. ...
5. Clean the Unit.

2.22 What are the step by step procedures in servicing automotive batteries?

2.22.1 Car Battery Care

1. Step 1: Clean the cables. Clean corrosion from the battery. ...
2. Step 2: Check the level of the electrolyte. ...
3. Step 3: Check the condition and charge of the battery. ...
4. Step 4: To drop in the new battery first remove the cables. ...
5. Step 5: Replace the battery. ...
6. Step 6: Reinstall the clamp and cables

2.23 STEERING SYSTEM

THE 5 FUNCTIONS OF A STEERING SYSTEM

33
 Following are some important functions of a car steering system:

 SETS YOUR CAR'S DIRECTION. ...

 GIVES STABILITY TO YOUR CAR. ...
 AVOIDS VIBRATIONS OF STEERING WHEEL. ...
 REDUCE TIRE WEAR. ...
 KEEPS YOUR CAR'S FRONT WHEELS STRAIGHT

2.24 How do you maintain a steering system?

 TIPS FOR POWER STEERING MAINTENANCE

1. Check Your Fluid Level Regularly. The easiest way to find a leak is by regularly checking
your fluid level. ...
2. Change Your Power Steering Filter Annually. ...
3. Have Your Power Steering Flushed, if Necessary. ...
4. Have Your Pump Checked for Damage. ...
5. Electric and Hydro-Electric Steering.

2.25 NEED OF STEERING SYSTEM MAINTENANCE

Improved Safety: The power steering system is a critical component of your vehicle. If it fails,
steering your car can become incredibly difficult, putting you and other drivers at risk. Regular
maintenance can help to ensure that your power steering system is always in good working order

 CAUSES STEERING SYSTEM FAILURE

34
Pump malfunctions, fluid leaks, blocked hoses, contamination of power steering fluid, or worn
power steering belts are some specific factors that can contribute to steering system failure

2.26 IMPROVES STEERING

 GET A ROUTINE ALIGNMENT.

Cars tend to veer slightly to one side or the other when alignment is off. If your tread doesn't look
the same on all tires (for example, the front tires look more worn down than the back ones), your
wheels are probably out of alignment

2.27 FACTORS AFFECT STEERING

Of all the factors affecting steering effort, following are identified as high influencing
parameters:
 Steering geometry.
 Steering system compliance.
 Friction in steering system linkages like assembly steering column, assembly steering gear
box etc.
 Tyre static friction torque

2.28 STEERING RATIO

 Typical automotive steering ratios range from about 24:1 with manual steering to about
14:1 with power steering assist. The higher the steering ratio, the easier it is to turn the
wheel and steer the vehicle. The lower the ratio is, the more effort is needed at the steering
wheel

2.28.1 STEERING SYSTEM MAINTENANCE

 Maintenance of the steering system consists of regular inspection, lubrication, and
35
 adjusting components to compensate for wear. When inspecting the steering system, you
will need someone to assist you by turning the steering wheel back and forth through the
free play while you check the steering linkage and connections. You will also be able to
determine if the steering mechanism is securely fastened to the frame.
 As light amount of free play may seem insignificant, but if allowed to remain, the free play
will quickly increase, resulting in poor steering control after prolonged use, steering
components can fail. t is important that the steering system be kept in good working
condition for obvious safety reasons. It is your job to find and correct any system
malfunctions quickly and properly
2.28.2 STEERING LINKAGE SERVICE
 Any area containing a ball-and-socket joint is subjected to extreme movements and dirt.
The combination of these two will cause the ball-and-socket joint to wear. When your
inspection finds sworn steering linkage components, they must be replaced with new
components. Two areas of concern are the idler arm and the tie-rod ends.

2.29 IDLER ARM SERVICE

 A worn idler arm cause’s play in the steering wheel. The front wheels, mostly the
right wheel, can turn without causing movement of the steering wheel. This is a very
common wear point in the steering linkage and should be checked carefully. To check an
idler arm for wear, grab the outer end of the arm (end opposite the frame) and force it up
and down by hand. Note the amount of movement atthe end of the arm and compare it to
the manufacturer’s specifications. Typically, an idler arm should NOT move up and down
more than 1/4 inch. The replacement of a worn idler arm is as follows: Separate the outer end
of the arm from the center link. A ball joint fork or puller can be used to force the idler arms
joint from the center link.

 With the outer end removed from the center link, unbolt and remove the idler arm from the
frame. Install the new idler arm in reverse order of removal. Make sure that all fasteners are
torqued to manufacturer’s specifications. Install a new cotter pin and bend it properly

2.30 MANUAL STEERING SYSTEM SERVICE

 Steering system service normally involves the adjusting or replacement of worn parts. Service
is required when the worm shaft rotates back and forth without normal pitman arm shaft
movement. This would indicate that there is play inside the gearbox. If excess clearance is not
corrected after the adjustments, the steering gearbox must be replaced or rebuilt.

2.31 THE MAINTENANCE OF ELECTRICAL

36
 Electrical maintenance is the process of ensuring that electrical equipment is kept in good
working order. It includes inspecting, testing, and repairing electrical equipment as necessary
to prevent problems that could lead to a loss of power or an electrical fire.

37
 UNIT – III
VEHICLE SYSTEM MAINTENANCE
HYDRAULIC BRAKE:

PRECAUTIONS:

 Always keep the brakes properly adjusted.

 Never allow the brake linings to wear down.
 Regularly inspect the fluid level in the reservoir and top up with brake fluid if necessary.
 Always exercise cleanliness when dealing with any part of hydraulic system.
 Never handle the internal hydraulic brake parts with greasy hands.
 Always use fresh brake fluid or alcohol for cleaning internal parts of the hydraulic system.
 One form of brake trouble that occurs frequently due to mineral oil contamination and it is usually
caused by topping up the hydraulic system with superior fluids (or) cleaning cylinders with petrol
during servicing.
 If the brake system has been contaminated, it is a dangerous condition and immediate attempt has
to be made to flush off all the brake fluid from the system and then refill with appropriate fluid.

BLEEDING OF HYDRAULIC SYSTEM:

 The process of removing the brake fluid from the hydraulic pipe line and cylinder is known as
bleeding. It is necessary whenever any part of the system is disconnected (or) fluid in the supply
tank exceeds the limit.
 Whenever seats are worn out it is possible for air to enter into the wheel cylinder without any sign
of leakage causing spongy pedal and it is the usual indication of air in the system.
 Never, under any circumstances use the fluid which has been bled from the system to top up the
supply tank because it may be aerated, have too much moisture content (or) be contaminated.

BLEEDING PROCEDURE:

 Before starting to bleed, follow the essential steps:

 Before commencing bleeding at each bleed screw, remove the dust cover and clean thoroughly. If
the master cylinder is fitted with bleeding screw, bleed the master cylinder first.
 Attach the bleed tube to wheel cylinder and then from the master cylinder to the glass jar
containing brake fluid.
 Open the bleed screw to 3/4th of a turn sufficient to the brake fluid to flow freely. Depress the
foot pedal slowly throughout full stroke of the pedal and allow it to return to its position slowly.
 There would be an interval of 3 to 4 seconds before making the next stroke.
 Repeat this action until the air bubbles seizes and then close the bleed screw immediately.
 While the pedal is thus held, securely tighten the bleed screw and remove the tube. Replace the
dust cover on the bleed screw. Repeat the same procedure on all the wheel cylinders.
 After the bleeding operation, top up the master cylinder reservoir with appropriate brake fluid to
a level of of 3/4th the reservoir and replace the filler cap.

38
BRAKE TESTERS:

 There are two types of brake testers, namely static and dynamic.
Static tester has four tread plates and registering columns. To remove the tests, the car is driven on
to the tread plates at specified speed and the brakes are applied hard.
 The stopping force at each wheel is registered on four columns. If the readings are too low, brake
service is needed.
 The dynamic brake tester has rollers in the floor. The two wheels for which brakes are to be tested
are placed on the rollers. If these are the drive wheels, the wheels are spun at specified speed by
vehicle engine. For non- driving wheels, the rollers and wheels are spun by electric motor. Then
the electric motor is switched off and the brakes are applied. The braking force at each wheel
registers on meters and based on the readings, service is performed

BRAKE SERVICE:

 Any complaint of faulty braking action, immediate measures have to be taken.

 Brake service includes:
 Addition of brake fluid
 Bleeding the hydraulic system to remove air
 Repair or replacement of master cylinder, wheel cylinders, etc.
 Replacement of brake linings Refinishing of brake drums

Overhauling of power-brake units.

WHEEL ALIGNMENT:

SERVICING STEERING LINKAGES AND SUSPENSION:

 If any defects are found, the causes must be determined and corresponding corrections must be
made before aligning the wheels.
 Servicing steering and suspension includes removal, replacement, adjustment of tie rods, removal
and replacement of other linkage parts.
 All of these services, if needed must be performed before aligning the

wheels. WHEEL ALIGNMENT:

 There are many types of wheel aligners. Some are mechanical types that attach to the wheel
spindles. Some have light beams that display the measurements on a screen in front of the car.
 When doing front wheel alignment, you should first check castor, camber, toe, turning radius, etc.
These are not adjustable. If they are out of specification it means parts are damaged and must be
replaced.
 Before you make alignment checks, the following pre-alignment inspections must be first made.
 Check and correct tyre pressure.
 Check and adjust wheel bearings.
 Check and adjust wheel run out.
 Check ball joints, if they are too loose, replace them.
39
  Check wheel balance, correct if necessary.
 Check front suspension height.
 Check shock absorbers and replace them if they are defective.
 Check wheel tracking.
This means whether rear wheels follow the front wheels. If the wheels are off the track, it usually
means frame is bent and it should be straightened

WHEEL BALANCE:

 The wheel may be checked for balance on or off the car.

 This is done in either of two ways: static or dynamic.
 In static balancing, the wheel is taken off the car and put on a ―bubble‖ balancer to
detect any imbalance.
 A wheel that is out of balance is heavier in one section. This will cause the bubble in the centre of
the balancer to move off the centre. To balance the wheel, weights are added to the wheel rim until
the bubble returns to centre.
 In dynamic balancing, the wheel is spun either on (or) off the car. An electronic wheel balancer is
used to balance a wheel on a car. Lack of balance shows up as a tendency for the wheel to move
off the centre (or) out of line as it spins. If the wheel is out of balance, one or more weights are
installed on the wheel rim.

ADJUSTING CAMBER AND CASTOR:

 By installing (or) removing shims.

 By turning a cam.
 By shifting inner shaft.
 By changing length of strut rod

ADJUSTING TOE:

After correcting camber and castor, toe is adjusted. Place the front wheels in straight-ahead position. Then
check the positions of the spokes in the steering wheel. If they are not centered, they can be properly
positioned when toe is set
TYRE MAINTENANCE:

The main purpose of tyres is that they have air-filled cushions that absorb most of the shocks caused by
road irregularities and secondly they grip the road to provide good traction. Good traction enables the car
to accelerate, brake, make turns without skidding. The main steps involved in tyre maintenance are:
Always maintain the recommended tyre inflation pressure.

 Do not overload the vehicle beyond the capacity prescribed by manufacturer.

 Avoid frequent sudden acceleration followed by sudden braking.
 Do regular checks like wheel alignment, condition of brakes, springs, wheels, etc.
 Regularly inspect the tread condition very closely since it is equally important like other
components.
 Retread the tyres promptly before they are completely defected.

40
  Replace the tyre before the tyre surface becomes

smooth CAUSES OF TYRE WEAR:

1. INFLATION PRESSURE:
 Over inflation or under inflation will cause rapid tyre wear. Over inflation results in wear of
the centre portion and under inflation results in wear of the shoulder.
2. TOE-IN OR TOE-OUT:
 The excessive toe-in shows feathered edges on inside edges.
 The excessive toe-out results in feathered edge wear on outside edges.
3. CAMBER:
 Too much positive camber results in excessive wear on the outer shoulders of the tyres. Too
much negative camber results in tyre wear of the inner shoulders
4. CASTOR:
 Excessive castor causes the spotting wear of tyres. Unequal castor causes the wheel to pull to
one side resulting in excessive and uneven wear.

TYRE FAILURE:

 The amount of wear a tyre gets depends upon its location of the car. For example on a car with rear
wheel drive, the right tyre wears twice as much as the left tyre. This is because many roads are
slightly crowned (higher in the centre) and also the right tyre is driving. The crown causes the car
to lean out a little so that the right tyre carries more weight.
 To equalize the wear as much as possible tyres should be rotated any time, uneven wear is noticed
as the distance specified by the manufacturer.
 One manufacturer recommends rotating radial tyres after 12000kms and then after every
24000kms. Bias tyres should be rotated every 12000kms.
 The amount of wear the tyre experiences depends upon its rotation on the car.
 On a car with rear wheel drive, the rear right tyre wears about twice as that of the rear left wheel.
 To equalize wear as much as possible, tyres should be rotated any time whenever eneven wear is
noticed and at the distance specified by the manufacturer.

TYPES OF TYRE WEAR:

1. TOE-IN OR TOE-OUT WEAR:

Excessive toe-in or toe-out on turns causes the tyre to be dragged sideways as it moves forward and
this scraps off rubber.
If both tyres show this type of wear, then toe is correct. But if only one tyre shows this type of wear,
steering arm should have been bent.
2. CAMBER WEAR:
If the wheel has excessive camber, the tire runs more on one shoulder than the other.
3. CORNERING WEAR:
This is caused by taking curves at high speeds producing diagonal type of wear.
4. UNEVEN TIRE WEAR:
It occurs due to various mechanical problems. These include misaligned wheels, over inflation of
tyres, unbalanced wheels, etc.
41
5. HIGH-SPEED WEAR:
Tyres wear more rapidly at high speed than at low speed. Tyres driven at 110-130km/hr will
experience only half the life of tyres driven at 50-60km/hr
TYRE INSPECTION:

 The purpose of inspecting the tyres is to determine whether they are safe for further use. When an
improper wear pattern is found, technician must know the cause for abnormal wear and should
correct the problem.
 If the tyres are in good condition they can be rotated
 While inspecting a tyre, check for bulges in the side walls. A bulge is a danger signal. It can
mean that plies are separated or broken and the tyre is likely to go flat. A tyre with bulge should be
removed.
 To make complete tyre inspection, remove all the stones from the tread. This is to ensure that no
tire damage is hidden by the stones.
 A quick way to check tread wear is with a Lincoln penny inserted in the tread grooves. Tread of
atleast 0.79mm is needed.
 A tyre can look okay from outside but it may have internal damage. To completely inspect a tire it
should be removed from the rim and then examine it closely, inside and out.

42
REMOVAL AND FITTING OF TYRE AND TUBE :

The procedure for the removal and fitting of tyre and tube is as below:

1) Loosen the wheel nuts of tyre to be removed.

2) Place the wedge before and after resting the three wheels to prevent vehicle from rolling.

3) Fix up jack and lift the vehicle to the extent that wheel is free from ground.

4) Remove the wheel after removing the wheel nuts.

5) Keep the wheel flat on ground and deflate it after removing valve with valve die.

6) Hammer the tyre at shoulder so that its bead is free from rim on both sides.

7) Press tyre lever between bead of tyre and rim flange.

8) Take another tyre lever; press it in the same way a little apart from the first lever.

9) Now press both levers down. By doing so some portion of tyre bead will come out of rim.

10) Pull out first lever and insert it again at some distance away from the second lever. Press it down.

11) Now go on changing the lever till tyre is out of the rim completely.

12) When one bead of tyre is out take out the tube after unscrewing valve body securing nut.

13) If tyre is to be completely replaced, proceed in the same way to remove the second bead.

14) In case, only tube is to be replaced, fix up the new tube.

15) Finally replace the tyre with caution using the levers and inflate it to correct

pressure.

43
STEERING SYSTEM TROUBLE SHOOTING:
COMPLAINTS POSSIBLE CAUSES CHECK(OR) CORRECTION

Readjust, replace worn parts

1. Excessive play in Looseness in steering gear Readjust, replace worn
steering
system Looseness in linkage parts
Loose wheel bearing Readjust
2. Hard steering Low tyre pressure Inflate to correct tyre
pressure
Friction in steering gear Lubricate, readjust, replace
worn parts
Friction in linkage Lubricate, readjust, replace
worn parts
Low or uneven Inflate to correct tyre pressure
3. Car wander pressure Readjust, lubricate, replace worn parts
Steering gear binding Readjust, lubricate, replace worn parts
Check alignment and
Linkage binding readjust

Incorrect wheel alignment

Inflate to correct tyre

4. Car pulls to one side Uneven tyre pressure pressure
during
normal driving Uneven castor or camber Check alignment, adjust
Wheel not tracking Check tracking, replace
defective parts
Readjust, replace brake lining
5. Car pulls to one Brakes grab Inflate to correct tyre pressure
Check alignment, adjust
side while braking
Uneven tyre pressure
Uneven castor or
camber
Inflate to correct tyre pressure
6. Front wheel shimmy Uneven tyre pressure Readjust, replace worn parts
at low Replace worn parts Balance the
pressure Loose linkage wheels
Loose ball joints
Dynamic
imbalance
Inflate to correct tyre pressure
7. Steering shakes Uneven tyre pressure Readjust, replace worn parts
Readjust, replace worn parts
Looseness in linkage Repair or replace

Looseness in steering
gear Shock absorber
defective
8. Tyres squeal on Excessive speed on curves Take curves at slow speed Inflate to
44 correct tyre pressure
turns(skids)
Uneven tyre pressure Check and adjust Replace tyres
Front alignment
incorrect Worn tyres
SUSPENSION SYSTEM TROUBLE SHOOTING:

COMPLAINT POSSIBLE CAUSES CHECK(OR)

CORRECTION

1. Hard or rough ride  Excessive tyre pressure  Readjust to correct

 Defective shock absorber pressure
Excessivefriction suspension  Repair (or) replace
spring  Lubricate, realign parts

2. Sway on turns  Loose stabilizer bar  Tighten it

 Sagging springs Castor  Repair or replace Adjust
incorrect

3. Spring breakage  Overloading  Avoid overloading

 Defective shock absorber  Repair or replace

 Loose U-bolts  Keep bolts tight

4. Sagging springs  Broken leaf  Replace

 Spring weak  Replace
 Defective shock absorber  Repair or replace

5. noises  Could co me from any loose,

worn(or) un lubricated part
in the
 suspension(or) steering
system

45
DESCRIPTION:

The wheel alignment refers to the positioning of the front wheels and steering mechanism that
gives the vehicle directional stability, promotes case of steering and reduces tyre wear to a minimum. A
vehicle is said to have directional stability or control if it can run straight down a road, enter and leave a
turn easily and resist road shocks. The front wheel alignment depends upon the following terms – Camber,
Caster, Kingpin inclination, toe- in and toe-out on turns. The front wheel geometry or steering geometry
refers to the angular relationship between the front wheels, the front wheel attaching parts and the vehicle
frame. All the above terms are included in the front wheel geometry. The various factors that affect the
wheel alignment of the vehicles are given below

1. Factors pertaining to wheel

a. Balance of wheels
b. Inflation of tyres
c. Brake adjustment
2. Steering Geometry
a. Camber
b. Caster
c. Kingpin inclination
d. Toe- in and Toe-out
3. Steering linkages
4. Suspension

System Camber

The angle between the centerline of the tyre and the vertical line when viewed from the front of the vehicle is
known as camber. When the angle is turned outward, so that the wheels are farther apart at the top than at the
bottom, the camber is positive. When the angle is inward, so that the wheels are closer together at the top than
at the bottom, the camber is negative. Any amount of camber, positive or negative, tends to cause uneven or
0.
more tyre wear on one side that on the other side. Camber should not Exceed 2

46
Procedu
re (i) Turn the wheelto 0 LHS
30
(ii) Adjust the sprit level such that the bubble occupies the center position.
(iii)(iv) Note the reading of the scale.
0
60 0
Turn the wheel to RHS and the above procedure is repeated and the
30 noted. value is
(v) The difference between the two readings gives the camber angle.

Caster

The angle between the vertical line and the kingpin centerline in the plane of the wheel
(when viewed from the side) is called the Caster angle. When the top of the king pin is
backward, the caster angle is positive and when it is forward the caster angle is negative.
The caster angle in modern vehicles range from 2 to 8 degrees.

Procedure

(i) Park the car on the turning table

(ii) Turn the wheel alignment gauge to 900.
(iii) Fix the wheel alignment gauge on the wheel.
(iv) Turn the wheel to 250 in RHS.

(v) Adjust the bubble to its original position

(vi) Note the reading on the 50-degree scale and the noted value will give the caster angle.

Kingpin inclination

The angle between the vertical line and center of the kingpin or steering axle, when viewed
47
from the front of the vehicle is known as kingpin inclination or steering axle inclination.
The kingpin inclination in combination with caster is used to provide directional stability in
modern cars, by tending to return the wheels to the straight-ahead position after any turn. It
also reduces steering effort particularly when the vehicle is stationary. It reduces tyre wear
also. The kingpin inclination in modern vehicles range from 4 to 8 degrees.
Procedure
(i) Park the car on the turntable.

(ii) Fix the wheel alignment gauge on the wheels.

(iii) Turn the wheel to 300 RHS and adjust the spirit level such that the bubble
occupies center position.

(iv) Note the value on the 600 scale and the value gives the kingpin inclination.

Toe- in and Toe-out

The front wheels are usually turned in slightly in front so that the distance between the front
ends

(A) is slightly less than the difference between the back ends (B), when viewed from the
top. The difference between these distances is called toe- in. The amount of toe- in usually
3 to 5 mm. The toe-in is provided to ensure parallel rolling of the front wheels, to stabilize
steering and prevent side slipping and excessive tyre wear.

Toe-out is the difference in angle between the two front wheels and the car frame during
turns. The steering system is designed to turn the inside wheel through a larger angle tha n
the outside wheel when making a turn. The condition causes the wheels to toe-out on turns,
due to difference in their turning angles. The toe-out is secured by providing the proper
relationship between the steering knuckle, tie-rods and pitman arm.

Procedure

(i) The toe-out bar is positioned from the front of the vehicle such that the pointer
touches the wheel and the distance between the wheels is found from the scale on the bar.
Keep is as (A).

(ii) Similarly the distance between the front wheels on the rear side is noted. Keep it as
(B).

(iii) From the readings we can find out toe- in or toe-out. If A > B, then it is toe-out and
48
 if B > A, then it is toe- in.
Toe-out on turns
(i) Park the car on the turn table.
(ii) Turn the wheel to extreme left.
(iii) The readings in both the turntable are noted. The difference in the reading will give
the toe-out on left turn.
(iv) Similarly the values are calculated for the right turn.

Wheel Bearing Tightening and

Adjustment Hoist the vehicle and
remove the rear wheel.
 Remove spindle cap by hammering at 3 or 4 locations.
 Remove the split pin, castle nut and washer.
 Check to ensure that the parking brake lever is not pulled up.
 Remove the back plate plug attached to the backside of brake plate, so as to
increase clearance between brake shoe and brake drum.
 Remove the wheel bearings.
 Insert the new stud in drum hole after rotating the stud slowly to assure the
serrations are aligned with these made by original bolt.
Ensure that all the nuts are tightened properly

BRAKE MAINTENANCE & REPAIR

Automobile braking systems are engineered to deliver precise movements to slow or stop your vehicle on
demand. When you apply the brake pedal, the master cylinder generates pressure through hydraulic
brake lines triggering brake pads or shoes to press against discs and/or drums that slow and stop your
vehicle.
The friction and heat generated wears down brake shoes, pads, calipers, rotors and other
brake components.
Brake Rotor Maintenance and/or Replacement
Brake rotors and brake pads are the two most renowned items in your vehicle's braking system. The rotors
are iron discs mounted to your wheel hubs which are gripped by brake pads or shoes encased in a caliper
system. Slots or circular holes may be found on your brake pads or on the rotors themselves which are
incorporated to circulate air to cool the brake system providing more effective braking while extending
rotor longevity.
Disc Brake Repair
Most modern-day vehicles are equipped with disc brakes in both the front and rear. Disc brake systems are
comprised of brake pads, calipers, rotors, and hydraulic components. Calipers squeeze brake pads against
rotors to slow or bring the vehicle to a stop in disc brake assemblies. Ventilation holes or slots may be
present on the rotors in order to help dissipate heat and cool the brake system. Although brake pads and
rotors require the most maintenance, any portion of the disc brake assembly may need attention from time-
to-time.
49
Drum Brake Repair
Certain vehicles are manufactured with rear drum brakes in place of rear disc brakes. Drum brake
assemblies consist of brake drums, shoes, wheel cylinders, springs and self-adjusters. Brake shoes rest
against the "drum" until the brakes are pressed sending brake fluid through the wheel cylinders against the
brake shoes which squeeze against the drum and creates stopping power. Upon release of the brake pedal,
the springs return the brake shoes back to their starting position. This self-adjusting system helps keep the
brake shoes in position when the brakes are not applied. As the brake shoes wear, a self-adjuster
compensates for the gap by moving the brake shoe closer to the brake drum.
Parking Brake Repair
A parking brake's sole function is to keep your vehicle stationary when parked, especially when parked on
steeper grades. Parking brakes are typically synonymous with "emergency brakes" since their use can be
for sudden stops to prevent accidents and operate mutually exclusive of the main braking system. A
parking brake check should be part of any routine brake inspection.

SUSPENSION SYSTEM SERVICE

A suspension system undergoes tremendous abuse during normal vehicle operation. Bumps and potholes
in the road surface cause constant movement, fatigue, and wear of the shock absorbers, or struts, ball
joints, bushings, springs, and other components.
Suspension system problems usually show up as abnormal noises (pops, squeaks, and clunks), tire wear,
steering wheel pull, or front end shimmy (side-to-side vibration). Suspension system wear can upset the
operation of the steering system and change wheel alignment angles. Proper service and maintenance of
these components greatly increase reliability and vehicle life.

MACPHERSON STRUT SERVICE

• Macpherson strut shock fails
– Common repair procedures
• Replace entire assembly
• Install a strut cartridge
• Some struts are easily removed at the bottom by removing two bolts
– Spring compressor is used to compress the coil spring
– Some struts can be serviced with a shock cartridge
• Inspect the upper strut bearing
• Inspect condition of upper strut bearing while strut is disassembled
• Install the coil spring
– Install coil spring and tighten locknut
– Be sure both ends of spring are correctly seated before removing compressor
• Reinstall in same position as before
50
 – Wheel alignment may be needed after strut replacement
– Brakes will need to be bled if brake caliper was disconnected
Coil Spring Service
• Characteristics
– Coil spring will rarely break unless it has been constantly overloaded or has a
stress raiser
– Incorrect ride height affects wheel alignment angles, camber, toe, SAI, and
scrub radius
– A vehicle that is too low cannot be aligned properly
• Adjusting spring height
– Correct ride height must be restored prior to alignment
– Coil springs must be replaced when they have sagged beyond specifications
• Coil spring replacement
– Replaced in front or rear pairs
– Replacement springs must be of the same kind
• Major considerations
– During a coil spring replacement: only lower ball joint needs to be removed
– Spring seats must be accurately aligned
– Torsion bar adjusting bolt must be loosened before removing torsion bar
– Leaf spring problems include broken leaves, spring sag, and differences in ride
height
Leaf spring service

Leaf springs are likely to wear because they have several moving parts. They should be
inspected at intervals specified by the car manufacturer, or at major service intervals -
usually every 12,000 miles (20,000 km).
The standard leaf spring is made from several thin strips of sprung steel of different lengths
and held together by clamps. It is subject to wear as the leaves rub against each other
during suspension movement. To overcome this, a tapered-profile single leaf spring is
fitted on some vehicles. Dirt particles between separate leaves accentuate wear and rust.
The springs should be kept fairly clean in order to extend their useful life. The intervals at
which this is done will be given in your car handbook. Modern leaf springs do not need
lubricating with oil — which may damage any anti-friction material between leaves. Spray
them instead with a silicone-based lubricant.

STEERING SYSTEM MAINTENANCE

Maintenance of the steering system consists of regular inspection, lubrication, and

adjusting components to compensate for wear. When inspecting the steering system,
you will need someone to assist you by turning the steering wheel back and forth through
51
 the free play while you check the steering linkage and connections. You will also be able to
determine if the steering mechanism is securely fastened to the frame.
As light amount of free play may seem insignificant, but if allowed to remain, the free play
will quickly increase, resulting in poor steering control after prolonged use, steering
components can fail. t is important that the steering system be kept in good working
condition for obvious safety reasons. It is your job to find and correct any system
malfunctions quickly and properly
Steering Linkage Service

Any area containing a ball-and-socket joint is subjected to extreme movements and dirt.
The combination of these two will cause the ball-and-socket joint to wear. When your
inspection finds sworn steering linkage components, they must be replaced with new
components. Two areas of concern are the idler arm and the tie-rod ends.

IDLER ARM SERVICE

A worn idler arm causes play in the steering wheel. The front wheels, mostly the
right wheel, can turn without causing movement of the steering wheel. This is a very
common wear point in the steering linkage and should be checked care fully.

To check an idler arm for wear, grab the outer end of the arm (end opposite the frame) and
force it up and down by hand. Note the amount of movement atthe end of the arm and
compare it to the manufacturer’s specifications. Typically, an idler arm should NOT
move up and down more than 1/4 inch.

The replacement of a worn idler arm is as follows:

Separate the outer end of the arm from the center link.
A ball joint fork or puller can be used to force the idler arms joint from the center link.

With the outer end removed from the center link, unbolt and remove the idler arm from the
frame. Install the new idler arm in reverse order of removal.

Make sure that all fasteners are torqued to manufacturer’s specifications. Install a new
cotter pin and bend it properly.

MANUAL STEERING SYSTEM SERVICE

Steering system service normally involves the adjusting or replacement of worn parts.
Service is required when the worm shaft rotates back and forth without normal
pitman arm shaft movement. This would indicate that there is play inside the gearbox. If
52
excess clearance is not corrected after the adjustments, the steering gearbox must be
replaced or rebuilt.

53
 UNIT – IV VEHICLE SAFETY

SAFETY EQUIPMENTS

Seat belt, regulations, automatic seat belt lightener system Collapsible steering column,
tilt able steering wheel
Air bags, electronic system for activating air bags Bumper design for safety

SEAT BELT
 A seat belt, sometimes called a safety belt, is a safety harness designed to

Figure 4.1. Three points seat belt.

 secure the occupant of a vehicle against harmful movement that may result
from a collision or a sudden stop.
 As part of an overall automobile passive safety system, seat belts are intended
to reduce injuries by stopping the wearer from hitting hard interior elements
of the vehicle, or other passengers (the so-called second impact), are in the
correct position for the airbag to deploy and prevent the passenger from
being thrown from the vehicle.
 Seat belts also absorb energy by being designed to stretch during an impact,
so that there is less speed differential between the passenger's body and their
vehicle interior, and also to spread the loading of impact on the passengers’
body.
 The final, so-called 'third impact' after a passenger's body hits the car
interior, airbag or seat belts, is that of the internal organs hitting the ribcage
or skull.
 The force of this impact is the mechanism through which car crashes cause
disabling or life threatening injury.

54
  The sequence of energy dissipating and speed reducing technologies - crumple
zone - seat belt - airbags - padded interior, are designed to work together as
system, to reduce the force of this final impact
Types of seat belts
 Lap seat belt
 Threepoints seatbelt Lap:
 Adjustable strap that goes over the waist. Used frequently in older cars, now
uncommon except in some rear middle seats. Passenger’s aircraft seats also
use lap seat belts to preventinjuries.
Sash:
 Adjustable strap that goes over the shoulder. Used mainly in the 1960s, but of
limited benefit because it is very easy to slip out of in a collision.
Three-point:
 Similar to the lap and shoulder, but one single continuous length of webbing.
Both three- point and lap-and-sash belts help spread out the energy of the
moving body in a collision over the chest, pelvis, and shoulders. Volvo
introduced the first production three-point belt in 1959. The first car with
three point belt was a Volvo PV 544 that was delivered to a dealer in Kristian
stad on August 13, 1959. The three point belt was developed by Nils Bohlin
who earlier had worked on ejection seats at Saab. Until the 1980s, three-point
belts were commonly available only in the front seats of cars; the back seats
had only lap belts or diagonal belts. Evidence of the potential for lap belts to
cause separation of the lumbar vertebrae and the sometimes associated
paralysis, or "seat belt syndrome", has led to a revision of passenger safety
regulations in nearly all developed countries requiring that all seats in a
vehicle be equipped with three-point belts. Since September 1, 2007, all new
cars sold in the U.S. require a lap and shoulder belt in the center rear.

Seat belts and seat-belt tighteners

Figure 4.2. Parts of Seat belt.

55
Figure 3.3. Occupant protection systems with belt tighteners and front airbags

FUNCTION:
The function of seat belts is to restrain the occupants of a vehicle in their seats when the
vehicle hits an obstacle.
Seat-belt tighteners improve the restraining characteristics of a three-point inertia-reel
belt and increase the protection against injury.
In the event of a frontal impact, they pull the seat belts tighter against the body and thus
hold the upper body as closely as possible against the seat backrest.
This prevents excessive forward displacement of the occupants caused by mass inertia.

Operating concept:
 In a frontal impact with a solid obstacle at a speed of 50 km/h, the seat belts
must absorb a level of energy comparable to the kinetic energy of a person in
free fall from the 4th floor of a building. Because of the belt slack, the belt
stretch and the delayed effect of the belt retractor ("film-reel effect"),three-
point inertia-reel belts provide only limited protection in frontal impacts with
solid obstacles at speeds of over 40 km/h because they can no longer safely
prevent the head and body from impacting against the steering wheel or the
instrument panel. An occupant experiences extensive forward displacement
without restraint systems.
 Deceleration to standstill and forward displacement of an occupant at an
impact speed of 50 km/h.1 Impact, 2 Firing of belt tightener/airbag, 3 Belt
tightened, 4 Airbag inflated. without/ with restraint systems. In an impact, the
shoulder belt tightener compensates for the belt slack and the "film-reel
effect" by retracting and tightening the belt strap.

56
  At an impact speed of 50 km/h, this system achieves its full effect within the
first 20 ms of the impact; and thus supports the airbag which needs approx.
40 ms to inflate completely. The occupant continues to move forward slightly
until making contact with the deflating airbag and in this manner is protected
from injury.
A prerequisite for optimum protection is that the occupants' forward movement away
from their seats remains minimal as they decelerate along with the vehicle. This is
achieved by triggering the belt tighteners immediately upon initial impact to ensure that
safe restraint of the occupants in the front seats starts as soon as possible.

The maximum forward displacement with tightened seat belts is approx. 1 cm and the
duration of mechanical tightening is 5...10 ms. On activation, a pyrotechnical propellant
charge is electrically fired. The explosive pressure acts on a piston, which turns the belt
reel via a steel cable in such a way that the belt rests tightly against the body.

Figure 3.4. Shoulder-belt tightener

1.Ignition cable, 2 Firing elements, 3 Propellant charge, 4 Piston, 5 Cylinder, 6 Metal

cables, 7 Belt reel, 8 Belt strap.

57
COLLAPSIBLE STEERING COLUMN
The collapsible steering column, like shoulder harnesses or air bags, is a device that
greatly increases driver survivability in the event of a head on collision. During a head on
crash, the steering column can be pushed into the passenger compartment with
tremendousforce.
At the same time, drivers obey Newton’s first law of motion and continue to travel at
the same speed of the automobile until something acts on the driver to slow or stop them.
Too frequently, it was the steering wheel that caused drivers to stop, sometimes with
horrific consequences.
In fact, years ago it was not unheard of for drivers to be impaled on the steering shaft.
As a result, engineers began to investigate ways in which driver survivability could be
increased for those unlucky enough to slam into the steering wheel. The goal was to
develop a system in which the driver could safely slow down or decelerate during a front
end collision. What they developed is now known as the collapsible steering column. Its
design was so successful that nearly all of today’s steering columns are designed to deform
under pressure from impact.
Collapsible steering columns come in a number of designs. Some columns integrate a
series of telescoping tubes that collapse when impacted by the driver. Others use break
points in the column that will allow the bend more easily. Still others have a special joint
near the steering gear that allows the column to snap down during impact. While air bags
have become more prominent over the past few years, collapsible steering columns
continue to play an important role in enhancing driver safety. But rather than being a
primary safety feature, steering column designs have come to represent the last ring of
safety behind shoulder harnesses restraints and air bags. Together, more drivers are
walking away from crashes that would have certainly resulted in death, just a few years
ago.

Figure 3.5. Parts of conventional steering column assembly

58
Figure 3.6. Parts of standard crushable steering column assembly

AIR BAGS, ELECTRONIC SYSTEM FOR ACTIVATING AIR BAGS:

Front airbag
Function:
The function of front airbags is to protect the driver and the front passenger against head
and chest injuries in a vehicle impact with a solid obstacle at speeds of up to 60 km/h.
In a frontal impact between two vehicles, the front airbags afford protection at relative
speeds of up to 100 km/h. A belt tightener alone cannot prevent the head from hitting the
steering wheel in response to severe impact. In order to fulfill this function, depending on
the installation location, vehicle type and structure-deformation response, airbag shave
different filling capacities and pressure build-up sequences adapted to the specific vehicle
conditions.
In a few vehicle types, front airbags also operate in conjunction with "inflatable knee
pads", which safeguard the "ride down benefit", i.e. the speed decrease of the occupants
together with the speed decrease of the passenger cell.
This ensures the rotational forward motion of the upper body and head which is
actually needed for optimal airbag protection, and is of particular benefit in countries
where seat- belt usage is not mandatory.

59
Figure 3.7. Construction and working of airbag.

60
Operating concept:
To protect driver and front passenger, pyrotechnical gas inflators inflate the driver and
passenger airbags in pyrotechnical, highly dynamic fashion after a vehicle impact
detected by sensors.
In order for the affected occupant to enjoy maximum protection, the airbag must be fully
inflated before the occupant comes into contact with it.
The airbag then responds to upper-body contact with partial deflation in a response
pattern calculated to combine "gentle" impact-energy absorption with non-critical (in
terms of injury) surface pressures and decelerative forces for the occupant. This concept
significantly reduces or even prevents head and chest injuries.
The maximum permissible forward displacement before the driver's airbag is fully
inflated is approx.12.5 cm, corresponding to a period of approx. 10 ms + 30 ms = 40 ms
after the initial impact (at 50 km/h with a solid obstacle) (see Fig. "Deceleration to
standstill"). It needs 10 ms for electronic firing to take place and 30ms for the airbag to
inflate.
In a 50 km/h crash, the airbag takes approx. 40 ms to inflate fully and a further 80...100
ms to deflate through the deflation holes. The entire process thus takes little more than a
tenth of a second, i.e. the batting of an eyelid.

Impact detection:
 Optimal occupant protection against the effects of frontal, offset, oblique or
pole impact is obtained through the precisely coordinated interplay of
electrically fired pyrotechnical front airbags and seat-belt tighteners.
 To maximize the effect of both protective devices, they are activated with
optimized time response by a common ECU (triggering unit) installed in the
passenger cell. The ECU's deceleration calculations are based on data from
one or two electronic acceleration sensors used to monitor the decelerative
forces that accompany an impact. The impact must also be analyzed. A
hammer blow in the workshop, gentle pushing, driving over a curbstone or a
pothole should not trigger the airbag. With this end in mind, the sensor
signals are processed in digital analysis algorithms whose sensitivity
parameters have been optimized with the aid of crash-data simulations.
 Depending on the impact type, the first trigger threshold is reached within
5...60 ms. the acceleration characteristics, which are influenced for instance
by the vehicle equipment and the body's deformation performance, are
different for each vehicle. They determine the setting parameters which are of
crucial importance for the sensitivity in the analysis algorithm (computing
process) and, in the end, for airbag and belt-tightener firing.
 Depending on the vehicle-manufacturer's production concept, the trigger
parameters and the extent of vehicle equipment can also be programmed into
the ECU at the end of the assembly line ("end-of-line programming" or "EoL
61
 programming").In order to prevent injuries caused by airbags or fatalities to
"out-of-position" occupants or to small children in Re board child seats, it is
essential that the front airbags are triggered and inflated in accordance with
the particular situations.
 The following improvement measures are available for this purpose 1.
Deactivation switches. These switches can be used to deactivate the driver or
passenger airbag. The airbag function states are indicated by special lamps.2.
In the USA, where there have been approx. 130 fatalities caused by airbags,
attempts are being made to reduce aggressive inflation by introducing
"depowered airbags".
 These are airbags whose gas-inflator power has been reduced by 20...30 %,
which itself reduces the inflation speed, the inflation severity and the risk of
injury to "out-of- position" occupants. "Depowered airbags" can thus be
depressed more easily by large and heavy occupants, i.e. they have a reduced
energy-absorption capacity. It is therefore essential above all with regard to
the possibility of severe frontal impacts for the occupants to fasten their
seatbelts.3. "Intelligent airbag systems".
 The introduction of improved sensing functions and control options for the
airbag inflation process, with the accompanying improvement of the
protective effect, is intended to result in a step-by-step reduction in the risk of
injury.

Acceleration sensors:
 Acceleration sensors for impact detection are integrated directly in the ECU
(belt tightener, front airbag)and mounted at selected points on the left and
right body sides (side airbag) or in the vehicle's front-end deformation area
(upfront sensors for "intelligent airbagsystems").
 The precision of these sensors is crucial in saving lives. They are generally
surface- micromechanical sensors consisting of fixed and moving finger
structures and spring pins. A special process is used to incorporate the
"spring/mass system" on the surface of a silicon wafer.
 Since the sensors only have low working capacitance (≈1 pF), it is necessary to
accommodate the evaluation electronics in the same housing so as to avoid
stray- capacitance and other forms of interference.

Gas inflators:
The pyrotechnical propellant charges of the gas inflators for generating the airbag
inflation gas (mainly nitrogen) and for actuating belt tighteners are activated by an
electrically operated firing element.

62
The gas inflator in question inflates the airbag with nitrogen. The driver's airbag
integrated in the steering-wheel hub (volume 35...67 l) or the passenger airbag installed in
the glove box (70...150 l) is inflated approx. 30 ms after firing.

Figure 3.8. Combined ECU for belt tighteners and front/side airbags
.

BUMPER DESIGN FOR SAFETY

A bumper is a shield made of steel, aluminum, rubber, or plastic that is mounted on the
front and rear of a passenger car. When a low speed collision occurs, the bumper system
absorbs the shock to prevent or reduce damage to the car
The front and rear of the vehicle should be protected in such a manner that low-speed
collisions will only damage the vehicle slightly, or not at all. Prescribed bumper evaluation
tests (US Part 581, Canada CMVSS 215, and ECE-R 42) specify minimum requirements
in terms of energy absorption and installed bumper height.

Figure 3.9. Front bumper of a car.

63
Bumper evaluation tests in accordance with US Part 581 (4 km/h barrier collision, 4 km/h
pendulum tests) must be passed by a bumper system whose energy absorber is of the no-
damage absorber type.
The requirements of the ECE standard are satisfied by plastically deformable retaining
elements located between the bumper and the vehicle body structure. In addition to sheet steel,
many bumpers are manufactured using fiber-reinforced plastics and aluminum sections

Figure 3.10. Cross sectional view of bumpers 1. Shock-absorber system, 2 Energy-absorbing

PUR-foam systems

TEXT / REFERENCE BOOKS

1. Powloski.J - “Vehicle Body Engineering” - Business books limited, London - 1969.
2. Ronald.K.Jurgen - “Automotive Electronics Handbook” - Second edition- McGraw-
Hill Inc., - 1999.
3. Johnson, W., and Mamalis, A.G., "Crashworthiness of Vehicles, MEP, London, 1995
4. Bosch - “Automotive Handbook” - 5th edition - SAE publication - 2000.

Further Reading:
1. George A. Peters and Barbara J. Peters, Automotive Vehicle Safety, Taylor &
Francis, 2003.
2. G.S. Daehn, Sustainable design and manufacture of lightweight vehicle structures,
in Alternative Fuels and Advanced Vehicle Technologies for Improved
Environmental Performance, 2014. https://doi.org/10.1533/9780857097422.2.433.
3. Paul M. Leonardi, Car Crashes without Cars, THE MIT Press, Massachusetts
Institute of Technology, 2012.
4. Ulrich Seiffert and Lothar Wech, Automotive Safety Handbook, Second Edition,
Society of Automotive Engineers, SAE International, 2003.
5. Ing. Konrad Reif Ed, Fundamentals of Automotive and Engine Technology, Bosh
Professional Automotive Information, Springer Vieweg, 2014.
64
 6. Hermann Winner, Stephan Hakuli, Felix Lotz, Christina Singer Eds., Handbook of
Driver Assistance Systems, Springer Reference, 2016.
7. Ulrich Seiffert, Mark Gonter, Integrated Automotive Safety Handbook, SAE
International, 2014. doi:10.427/R-407.

What are the concepts of safety?

the prevention and control of injuries and other consequences or harm caused by accidents; the respect of the
values and the physical, material and psychological integrity of individuals;

THE CONCEPT OF VEHICLE SAFETY?

Automotive safety is the study and practice of automotive design, construction, equipment and regulation to
minimize the occurrence and consequences of traffic collisions involving motor vehicles. Road traffic safety
more broadly includes roadway design.

THE DIFFERENT TYPES OF SAFETY SYSTEMS IN VEHICLES

Head-Up Display (HUD), Anti-Lock Braking Systems (ABS), Electronic Stability Control (ESC), Tire Pressure
Monitoring System (TPMS), Lane Departure Warning System (LDWS), Adaptive Cruise Control (ACC), Driver
Monitoring System (DMS), Blind Spot Detection (BSD) and Night Vision System (NVS) are common Active Safety.

THE MOST IMPORTANT SAFETY FEATURE IN THE VEHICLE

Airbags are one of the most essential features in a car and a staple of motorist safety. These inflatable cushions are
designed to protect passengers in the event of a collision by deploying quickly and providing a barrier between the
passenger's head and the hard surfaces of the car.

THE FIVE MOST IMPORTANT SAFETY FEATURES FOR CARS

 #1 – Airbags. ...
 #2 – Forward Collision Warning and Braking. ...
 #3 – Blind spot monitoring. ...
 #4 – Lane Keep Assist. ...
 #5 – Inattentive driving monitor

SEAT BELT

A seat belt, also known as a safety belt or spelled seatbelt, is a vehicle safety device designed to secure the driver or a
passenger of a vehicle against harmful movement that may result during a collision or a sudden stop. A seat belt
reduces the likelihood of death or serious injury in a traffic collision by reducing the force of secondary impacts with
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interior strike hazards, by keeping occupants positioned correctly for maximum effectiveness of the airbag (if
equipped), and by preventing occupants being ejected from the vehicle in a crash or if the vehicle rolls over.

When in motion, the driver and passengers are traveling at the same speed as the vehicle. If the vehicle suddenly
stops or crashes, the occupants continue at the same speed the vehicle was going before it stopped. A seatbelt applies
an opposing force to the driver and passengers to prevent them from falling out or making contact with the interior of
the car (especially preventing contact with, or going through, the windshield). Seatbelts are considered primary
restraint systems (PRSs), because of their vital role in occupant safety.

Types

Two-point

A two-point belt attaches at its two endpoints. A simple strap was first used March 12, 1910,
by pilot Benjamin Foulois,[19][20][21] a pioneering aviator with the Aeronautical Division, U.S.
Signal Corps, so he might remain at the controls during turbulence.

The Irvin Air Chute Company made the seat belt for use by professional race car driver
Barney Oldfield when his team decided the daredevil should have a "safety harness" for the
1923 Indianapolis 500.[22][23][24]

Lap

A lap belt is a strap that goes over the waist. This was the most common type of belt prior to
legislation requiring three-point belts and is found in older cars. Coaches are equipped with
lap belts (although many newer coaches have three-point belts), as are passenger aircraft seats.

University of Minnesota professor James J. (Crash) Ryan was the inventor of, and held the
patent for, the automatic retractable lap safety belt. Ralph Nader cited Ryan's work in Unsafe
at Any Speed and, following hearings led by Senator Abraham Ribicoff, President Lyndon
Johnson signed two bills in 1966 requiring safety belts in all passenger vehicles starting in
1968.[25][26]

Until the 1980s, three-point belts were commonly available only in the front outboard seats of
cars; the back seats were often only fitted with lap belts. Evidence of the potential of lap belts
to cause separation of the lumbar vertebrae and the sometimes-associated paralysis, or "seat
belt syndrome" led to the progressive revision of passenger safety regulations in nearly all
developed countries to require three-point belts, first in all outboard seating positions, and
eventually in all seating positions in passenger vehicles. Since September 1, 2007, all new cars
sold in the US require a lap and shoulder belt in the center rear seat.[27] In addition to
regulatory changes, "seat belt syndrome" has led to a liability for vehicle manufacturers. One
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Los Angeles case resulted in a $45 million jury verdict against Ford; the resulting $30 million
judgment (after deductions for another defendant who settled prior to trial) was affirmed on
appeal in 2006.[28]

Sash

A "sash" or shoulder harness is a strap that goes diagonally over the vehicle occupant's
outboard shoulder and is buckled inboard of his or her lap. The shoulder harness may attach
to the lap belt tongue, or it may have a tongue and buckle completely separate from those of
the lap belt. Shoulder harnesses of this separate or semi-separate type were installed in
conjunction with lap belts in the outboard front seating positions of many vehicles in the North
American market starting at the inception of the shoulder belt requirement of the US National
Highway Traffic Safety Administration's (NHTSA) Federal Motor Vehicle Safety Standard
208 on January 1, 1968. However, if the shoulder strap is used without the lap belt, the vehicle
occupant is likely to "submarine", or slide forward in the seat and out from under the belt, in
a frontal collision. In the mid-1970s, three-point belt systems such as Chrysler's "Uni-Belt"
began to supplant the separate lap and shoulder belts in American-made cars, though such
three-point belts had already been supplied in European vehicles such as Volvo, Mercedes-
Benz, and Saab for some years.

Three-point

A three-point belt is a Y-shaped arrangement, similar to the separate lap and sash belts, but
unified. Like the separate lap-and-sash belt, in a collision, the three-point belt spreads out the
energy of the moving body over the chest, pelvis, and shoulders. Volvo introduced the first
production three-point belt in 1959.[29] The first car with a three-point belt was a Volvo PV 544
that was delivered to a dealer in Kristianstad on August 13, 1959. However, the first car model
to have the three-point seat belt as a standard item was the 1959 Volvo 122, first outfitted with
a two-point belt at initial delivery in 1958, replaced with the three-point seat belt the following
year.[30] The three-point belt was developed by Nils Bohlin who had earlier also worked on
ejection seats at Saab.[31] Volvo then made the new seat belt design patent open in the interest
of safety and made it available to other car manufacturers for free.[32][33]

Belt-in-Seat

The Belt-in-Seat (BIS) is a three-point harness with the shoulder belt attached to the seat itself,
rather than to the vehicle structure. The first car using this system was the Range Rover
Classic, which offered BIS as standard on the front seats from 1970.[34] Some cars like the
Renault Vel Satis use this system for the front seats. A General Motors assessment concluded
seat-mounted three-point belts offer better protection especially to smaller vehicle occupants,

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[35]
though GM did not find a safety performance improvement in vehicles with seat-mounted
belts versus belts mounted to the vehicle body.[36]

Belt-in-Seat type belts have been used by automakers in convertibles and pillarless hardtops,
where there is no "B" pillar to affix the upper mount of the belt. Chrysler and Cadillac are
well known for using this design. Antique auto enthusiasts sometimes replace original seats in
their cars with BIS-equipped front seats, providing a measure of safety not available when
these cars were new. However, modern BIS systems typically use electronics that must be
installed and connected with the seats and the vehicle's electrical system in order to function
properly.[citation needed]

4-, 5-, and 6-point

Five-point harnesses are typically found in child safety seats and in racing cars. The lap
portion is connected to a belt between the legs and there are two shoulder belts, making a total
of five points of attachment to the seat. A 4-point harness is similar, but without the strap
between the legs, while a 6-point harness has two belts between the legs. In NASCAR, the 6-
point harness became popular after the death of Dale Earnhardt, who was wearing a five-point
harness when he suffered his fatal crash; as it was first thought that his belt had broken, and
broke his neck at impact, some teams ordered a six-point harness in response.[37]

Seven-point

Aerobatic aircraft frequently uses a combination harness consisting of a five-point harness

with a redundant lap-belt attached to a different part of the aircraft. While providing
redundancy for negative-g maneuvers (which lift the pilot out of the seat), they also require the
pilot to un-latch two harnesses if it is necessary to parachute from a failed aircraft.

Seatbelt airbag

Seatbelt airbags are available in some models of Ford and Mercedes.

AUTOMATIC

SEATBELTS THAT AUTOMATICALLY MOVE INTO POSITION AROUND A VEHICLE

OCCUPANT ONCE THE ADJACENT DOOR IS CLOSED AND/OR THE ENGINE IS STARTED
WERE DEVELOPED AS A COUNTERMEASURE AGAINST LOW USAGE RATES OF MANUAL
SEAT BELTS, PARTICULARLY IN THE UNITED STATES. THE 1972 VOLKSWAGEN ESVW1
EXPERIMENTAL SAFETY VEHICLE PRESENTED PASSIVE SEAT BELTS.[50] VOLVO TRIED TO
DEVELOP A PASSIVE THREE POINT SEATBELT. IN 1973, VOLKSWAGEN ANNOUNCED
THEY HAD A FUNCTIONAL PASSIVE SEAT BELT.[51] THE FIRST COMMERCIAL CAR TO USE
AUTOMATIC SEAT BELTS WAS THE 1975 VOLKSWAGEN GOLF.[52]
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AUTOMATIC SEAT BELTS RECEIVED A BOOST IN THE UNITED STATES IN 1977 WHEN
BROCK ADAMS, UNITED STATES SECRETARY OF TRANSPORTATION IN THE CARTER
ADMINISTRATION, MANDATED THAT BY 1983 EVERY NEW CAR SHOULD HAVE EITHER
AIRBAGS OR AUTOMATIC SEAT BELTS.[53][54] THERE WAS STRONG LOBBYING AGAINST THE
PASSIVE RESTRAINT REQUIREMENT BY THE AUTO INDUSTRY.[55] ADAMS WAS CRITICIZED
BY RALPH NADER, WHO SAID THAT THE 1983 DEADLINE WAS TOO LATE.[56] THE
VOLKSWAGEN RABBIT ALSO HAD AUTOMATIC SEAT BELTS,[56] AND VW SAID THAT BY
EARLY 1978, 90,000 CARS HAD SOLD WITH THEM.[52]

GENERAL MOTORS INTRODUCED A THREE-POINT NON-MOTORIZED PASSIVE BELT

SYSTEM IN 1980 TO COMPLY WITH THE PASSIVE RESTRAINT REQUIREMENT.[57]
HOWEVER, IT WAS USED AS AN ACTIVE LAP-SHOULDER BELT BECAUSE OF UNLATCHING
THE BELT TO EXIT THE VEHICLE.[57] DESPITE THIS COMMON PRACTICE, FIELD STUDIES
OF BELT USE STILL SHOWED AN INCREASE IN WEARING RATES WITH THIS DOOR-
MOUNTED SYSTEM.[57] GENERAL MOTORS BEGAN OFFERING AUTOMATIC SEAT BELTS
ON THE CHEVROLET CHEVETTE.[58][59] HOWEVER, THE COMPANY REPORTED
DISAPPOINTING SALES BECAUSE OF THIS FEATURE.[60] FOR THE 1981 MODEL YEAR, THE
NEW TOYOTA CRESSIDA BECAME THE FIRST CAR TO OFFER MOTORIZED AUTOMATIC
PASSIVE SEATBELTS.[61]

A STUDY RELEASED IN 1978 BY THE UNITED STATES DEPARTMENT OF TRANSPORTATION

SAID THAT CARS WITH AUTOMATIC SEAT BELTS HAD A FATALITY RATE OF .78 PER 100
MILLION MILES, COMPARED WITH 2.34 FOR CARS WITH REGULAR, MANUAL BELTS.[62]

IN 1981, DREW LEWIS, THE FIRST TRANSPORTATION SECRETARY OF THE REAGAN

ADMINISTRATION, INFLUENCED BY STUDIES DONE BY THE AUTO INDUSTRY,[63]
DROPPED THE MANDATE;[64] THE DECISION WAS OVERRULED IN A FEDERAL APPEALS
COURT THE FOLLOWING YEAR,[65] AND THEN BY THE SUPREME COURT.[66] IN 1984, THE
REAGAN ADMINISTRATION REVERSED ITS COURSE,[67] THOUGH IN THE MEANTIME THE
ORIGINAL DEADLINE HAD BEEN EXTENDED; ELIZABETH DOLE, THEN TRANSPORTATION
SECRETARY, PROPOSED THAT THE TWO PASSIVE SAFETY RESTRAINTS BE PHASED INTO
VEHICLES GRADUALLY, FROM VEHICLE MODEL YEAR 1987 TO VEHICLE MODEL YEAR
1990, WHEN ALL VEHICLES WOULD BE REQUIRED TO HAVE EITHER AUTOMATIC SEAT
BELTS OR DRIVER SIDE AIR BAGS.[66] THOUGH MORE AWKWARD FOR VEHICLE
OCCUPANTS, MOST MANUFACTURERS OPTED TO USE LESS EXPENSIVE AUTOMATIC
BELTS RATHER THAN AIRBAGS DURING THIS TIME PERIOD.

WHEN DRIVER SIDE AIRBAGS BECAME MANDATORY ON ALL PASSENGER VEHICLES IN

MODEL YEAR 1995[CITATION NEEDED], MOST MANUFACTURERS STOPPED EQUIPPING CARS

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WITH AUTOMATIC SEAT BELTS. EXCEPTIONS INCLUDE THE 1995–96 FORD
ESCORT/MERCURY TRACER AND THE EAGLE SUMMIT WAGON, WHICH HAD AUTOMATIC
SAFETY BELTS ALONG WITH DUAL AIRBAGS.[CITATION NEEDED]

SYSTEMS

 MANUAL LAP BELT WITH AUTOMATIC MOTORIZED SHOULDER BELT—WHEN THE

DOOR IS OPENED, THE SHOULDER BELT MOVES FROM A FIXED POINT NEAR THE
SEAT BACK ON A TRACK MOUNTED IN THE DOOR FRAME OF THE CAR TO A POINT
AT THE OTHER END OF THE TRACK NEAR THE WINDSHIELD. ONCE THE DOOR IS
CLOSED AND THE CAR IS STARTED, THE BELT MOVES REARWARD ALONG THE
TRACK TO ITS ORIGINAL POSITION, THUS SECURING THE PASSENGER. THE LAP
BELT MUST BE FASTENED MANUALLY.

 MANUAL LAP BELT WITH AUTOMATIC NON-MOTORIZED SHOULDER BELT—THIS

SYSTEM WAS USED IN AMERICAN-MARKET VEHICLES SUCH AS THE HYUNDAI
EXCEL AND VOLKSWAGEN JETTA. THE SHOULDER BELT IS FIXED TO THE AFT
UPPER CORNER OF THE VEHICLE DOOR AND IS NOT MOTORIZED. THE LAP BELT
MUST BE FASTENED MANUALLY.

 AUTOMATIC SHOULDER AND LAP BELTS—THIS SYSTEM WAS MAINLY USED IN

GENERAL MOTORS VEHICLES, THOUGH IT WAS ALSO USED ON SOME HONDA
CIVIC HATCHBACKS AND NISSAN SENTRA COUPÉS. WHEN THE DOOR IS OPENED,
THE BELTS GO FROM A FIXED POINT IN THE MIDDLE OF THE CAR BY THE FLOOR
TO THE RETRACTORS ON THE DOOR. PASSENGERS MUST SLIDE INTO THE CAR
UNDER THE BELTS. WHEN THE DOOR CLOSES, THE SEAT BELT RETRACTS INTO
THE DOOR. THE BELTS HAVE NORMAL RELEASE BUTTONS THAT ARE SUPPOSED
TO BE USED ONLY IN AN EMERGENCY, BUT IN PRACTICE ARE ROUTINELY USED IN
THE SAME MANNER AS MANUAL SEAT BELT CLASPS.[CITATION NEEDED] THIS SYSTEM
ALSO FOUND USE BY AMERICAN SPECIALTY CARS WHEN THEY CREATED THE 1991-
1994 CONVERTIBLE SPECIAL EDITION OF THE NISSAN 240SX, A CAR THAT
TRADITIONALLY HAD A MOTORIZED SHOULDER BELT.

DISADVANTAGES

AUTOMATIC BELT SYSTEMS GENERALLY OFFER INFERIOR OCCUPANT CRASH

PROTECTION.[68][69] IN SYSTEMS WITH BELTS ATTACHED TO THE DOOR RATHER THAN A
STURDIER FIXED PORTION OF THE VEHICLE BODY, A CRASH THAT CAUSES THE
VEHICLE DOOR TO OPEN LEAVES THE OCCUPANT WITHOUT BELT PROTECTION. IN

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SUCH A SCENARIO, THE OCCUPANT MAY BE THROWN FROM THE VEHICLE AND SUFFER
GREATER INJURY OR DEATH.[69]

BECAUSE MANY AUTOMATIC BELT SYSTEM DESIGNS COMPLIANT WITH THE US PASSIVE-
RESTRAINT MANDATE DID NOT MEET THE SEATBELT ANCHORAGE REQUIREMENTS OF
CANADA (CMVSS 210) — WHICH WERE NOT WEAKENED TO ACCOMMODATE AUTOMATIC
BELTS — VEHICLE MODELS WHICH HAD BEEN ELIGIBLE FOR EASY IMPORTATION IN
EITHER DIRECTION ACROSS THE US-CANADA BORDER WHEN EQUIPPED WITH MANUAL
BELTS BECAME INELIGIBLE FOR IMPORTATION IN EITHER DIRECTION ONCE THE US
VARIANTS OBTAINED AUTOMATIC BELTS AND THE CANADIAN VERSIONS RETAINED
MANUAL BELTS. TWO PARTICULAR MODELS AFFECTED WERE THE DODGE SPIRIT AND
PLYMOUTH ACCLAIM.[70]

AUTOMATIC BELT SYSTEMS ALSO PRESENT SEVERAL OPERATIONAL DISADVANTAGES.

MOTORISTS WHO WOULD NORMALLY WEAR SEAT BELTS MUST STILL FASTEN THE
MANUAL LAP BELT, THUS RENDERING REDUNDANT THE AUTOMATION OF THE
SHOULDER BELT. THOSE WHO DO NOT FASTEN THE LAP BELT WIND UP INADEQUATELY
PROTECTED ONLY BY THE SHOULDER BELT. IN A CRASH, WITHOUT A LAP BELT, SUCH A
VEHICLE OCCUPANT IS LIKELY TO "SUBMARINE" (BE THROWN FORWARD UNDER THE
SHOULDER BELT) AND BE SERIOUSLY INJURED.[CITATION NEEDED] MOTORIZED OR DOOR-
AFFIXED SHOULDER BELTS HINDER ACCESS TO THE VEHICLE, MAKING IT DIFFICULT
TO ENTER AND EXIT—PARTICULARLY IF THE OCCUPANT IS CARRYING ITEMS SUCH AS A
BOX OR A PURSE. VEHICLE OWNERS TEND TO DISCONNECT THE MOTORIZED OR DOOR-
AFFIXED SHOULDER BELT TO RELIEVE THE NUISANCE WHEN ENTERING AND EXITING
THE VEHICLE, LEAVING ONLY A LAP BELT FOR CRASH PROTECTION.[CITATION NEEDED] ALSO,
MANY AUTOMATIC SEAT BELT SYSTEMS ARE INCOMPATIBLE WITH CHILD SAFETY SEATS,
OR ONLY COMPATIBLE WITH SPECIAL MODIFICATIONS.

Collapsible Steering Column Working Explained

The collapsible steering column is a type of advanced steering column. It is a part of the passive
safety system in cars. Most passenger vehicles commonly employ the collapsible version instead of
the regular steering column. It is also known as ‘Energy absorbing steering column’. Engineers
invented it to reduce the risk of injuries occurring to the driver in case of frontal impacts.

The function of a typical steering column is to transfer the motion of steering wheel to ground
wheels of the vehicle. It does this through the steering gearbox and respective linkages. The earlier

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generation of vehicles used a solid shaft in the steering column. Even though it served the purpose
well, it had a drawback in terms of a safety threat.

The engineers conducted several studies on the subject. In case such a vehicle confronts a severe
frontal impact, then the solid rod of steering column hurts the head and rib cage of the driver. Thus,
it elevates the severity of injuries. This is the main reason why automotive engineers invented the
collapsible-steering columns. They protect the drivers from possible injuries.
From the structural point of view, the collapsible column has a ‘tube within a tube’ type of structure.
It consists of hollow tubes of steel fitted into each other with the help of a special bearing and
sealing. When the vehicle meets a frontal impact of a sever intensity, this tube structure collapses
and absorbs the energy of impact. Thus, it considerably reduces the risk of damage to the driver’s
body.

THE MOST IMPORTANT ADVANTAGE OF COLLAPSIBLE STEERING COLUMN

Safety. Traditionally, cars feature a collapsible steering column (energy absorbing steering column) which will
collapse in the event of a heavy frontal impact to avoid excessive injuries to the driver.

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 AIRBAG

the principle of airbag

Air bags inflate when a sensor detects a front-end crash severe enough to trigger their deployment. The
sensor sends an electric signal to start a chemical reaction that inflates the air bag with harmless nitrogen gas.
All this happens faster than the blink of an eye.

What are the 3 main parts of an airbag?

The airbag module contains both an inflator unit and the lightweight fabric airbag. The airbag system consists
of three basic parts: (1) An airbag module, (2) crash sensors, and (3) a diagnostic unit. Some systems may
also have an on/off switch, which allows the airbag to be deactivated.

What is the purpose of airbags?

Airbags are inflatable cushions built into a vehicle that protect occupants from hitting the vehicle interior or
objects outside the vehicle (for example, other vehicles or trees) during a collision. The instant a crash
begins, sensors start to measure impact severity

What are the contents of air bags?

Air bags are inflated by nitrogen gas which is produced by the highly toxic chemical, sodium azide. However,
the sodium azide is completely consumed by this reaction. After deflation of the bag some irritant dusts
(including sodium hydroxide) are released

the two types of airbags?

There are 2 types of airbags. First is the torso airbag which protects your torso and the second is the
curtain airbag which deploys from the car ceiling protecting your head. Typically deploy from the steering
wheel to protect the driver from striking other parts of the car in a frontal crash.

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 UNITV

UNIT V
Design of the body for safety
Energy equation
Engine location
Deceleration of vehicle inside passenger compartment
Deceleration on impact with stationary and movable obstacle
Concept of crumble zone
Safety sandwich construction

INTRODUCTION:
 Automobile safety is the study and practice of design cars, construction, equipment
and regulation to minimize the occurrence and consequences of traffic collisions.

CRASHWORTHINESS:

Crashworthiness is also highly dependent on how the materials, construction and design of the
vehicle work together. From a collision point of view, a vehicle can be considered as two primary kinds
of structure. First, there is the passenger cabin, within which the occupants should be belted to the
seating. This compartment should represent a ‘safety cage’. Ideally this cage will not distort or deform.
Trapping feet with a collapsing firewall or having the roof structure deform onto heads is extremely
poor from an injury point of view. Very strong passenger compartments are essential for these safety
cages. The present material of choice for primary structural pillars is boron-containing hot stamped
steels, which have very high strength and are easily manufacturable. The other important element is the
crush zone that surrounds the cabin. This zone is tuned to absorb energy and provide deformation. Crash
performance is improved by controlling the acceleration of an occupant’s chest and minimizing a head
injury criterion, which is also related to peak rates of acceleration or G-loading. Vehicle safety standards
are based on these measures. To receive a 5-star crash rating, a passenger’s chest should receive fewer
than 48 Gs of acceleration when a vehicle impacts with a fixed rigid barrier. Therefore, from a design
point of view, the crush zone should crush from its original shape to nearly zero thickness in front of the
cabin compartment, ideally with a nearly constant force that is no greater than 48 times the vehicle
weight while the safety cage remains undeformed. For the deforming members, high strength or
stiffness is not desired, but what is important is the ability to absorb energy in a controlled manner and
the ability to crush the full distance from the bumper to cabin, while the force remain near the peak
value it maximizes the energy absorbed. Governmental regulation impose strict standards on occupant
protection, and on various crash modes including side impact and roof crush. The mass of vehicles
could be dramatically reduced if crashworthiness were not a consideration.

TYPES OF IMPACTS IN CAR ACCIDENTS:

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The impacts in car accidents are of three types.
VEHICLE IMPACT: The initial strike involves the exterior of the vehicle crashing into something, such as
another vehicle. Factors to consider here are the weight of the vehicles or objects, the speed of travel, and
how fast the vehicle stopped. These factors all dictate the force exerted, with speed being the one that has
the largest potential impact. The weight of a vehicle proportionally heightens the amount of force;
however, speed does so exponentially, thus it greatly affects the potential severity. Older vehicles were
traditionally designed to be resistant to forces in a collision, but in recent years the vehicles are instead
manufactured to better absorb the force and keep the passenger area better protected.
1. BODY IMPACT The second impact is the result of the occupant’s body striking something inside of
the vehicle. The body will typically be thrust toward the point of exterior impact and either be
restrained by a seat belt or stopped by striking an inside object—both of which are dangerous. It is
also critical to remember that any unsecured objects within the vehicle may also become
potentially damaging projectiles. Examples of such objects may include a glass beverage container,
a briefcase, or a tool box.
2. ORGAN IMPACT: The third impact relates to the damage occurring inside of the body, such as to
the internal organs. A common example occurs when your brain abruptly strikes the skull that
surrounds it. Organs that are solidly composed like the spleen or liver may be fractured and suffer
harmful bleeding. Key vessels like the aorta could be damaged, which is largely responsible for
blood flow, creating a potentially deadly situation.

DESIGN OF VEHICLE BODY FOR SAFETY

 The safety of a vehicle and its passengers can be improved by properly designing and
selecting the material for vehicle bodies.
 The vehicle body structure is subjected to static and dynamic service loads during the
life cycle. It also has to maintain its integrity and provide adequate protection in
survivable crashes.
 At present there are two designs of vehicle body constructions: 1. Body over frame
structure and 2. Uni- body structure.

Necessary features of a safe vehicle body:

 Deformable yet stiff front structure with crumple zones to absorb the crash kinetic
energy from frontal collisions
 Deformable rear structure to safeguard rear passenger compartment and protect the
fuel tank
 Properly designed side structures and doors to minimize intrusion in side impact
and prevent doors from opening due to crash loads
 Strong roof structure for rollover protection
 Properly designed restraint systems with working in harmony with the vehicle structure
 Accommodate various chassis designs for different power train locations and drive
train configurations.

Design techniques/strategies:
The following design techniques/strategies are to be followed while designing a car body
(especially front structure) to reduce the impact of crash and increase the safety of the car and
passengers.

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 Desired dummy performance:
 Dummy is a physical model representing humans inside a car.
 To model a car for safety, it should be modeled for proper crash energy management.
3. As the human beings are to be safeguarded, the interaction of the human beings with

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  the restraint system during a crash has to be studied first. This branch of study is widely
known as bio-mechanics.
 The reaction of a human being for a crash pulse has to defined and studied in depth.
The following steps are involved in this procedure

Stiff cage structural concept:

 Stiff cage is the passenger compartment structure which provides protection for the
passengers in all modes of survivable collisions.
 The necessary features of a good stiff cage structure are: 1. sufficient peak load capacity
to support the energy absorbing members in front of it, 2. High crash energy absorption.
The stiff cage structure should withstand all the extreme loads and the severe
deformation.
Controlled progressive crush and deformation with limited intrusion:
 To make the impact of crash less, the crush event has to be controlled and the
deformation should be made such that the intrusion of other components into the
passenger compartment is less.
 Axial mode of crush is preferred to bending mode of crush as bending mode has lower
energy content.
 To achieve this objective three different crush zones are identified:
o Soft front zone: Reduces the aggressively of crash in pedestrian / vehicle and
vehicle / vehicle collisions
o Primary crush zone: It consists of the main energy absorbing structure before the
power train. It is characterized by a relatively uniform progressive structural
collapse.
o Secondary crush zone: Lies between the primary zone and passenger
compartment and sometimes extends into the passenger compartment up to
firewall. It provides a stable platform for the primary zone and transfers the load
to the occupant compartment as efficiently as possible.
Weight efficient energy absorbing structures:
 The architecture of the structural frame (structural topology) design depends on the
ability to design the primary crush zone for bending, folding, mixed folding and bending.
 For a given vehicle package different topologies have to be studied for the same crush
energy absorption. The steps followed are:
 Create a simple model of vehicle front end system
 Determine the design loads of structural members

ENERGY EQUATION

 The application of the conservation of energy principle provides a powerful tool

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 for problem solving.
 Newton's laws are used for the solution of many standard problems, but often there
are methods using energy which are more straightforward.
 The basic reason for the advantage of the energy approach is that just the beginning
and ending energies need be considered; intermediate processes do not need to be
examined in detail since conservation of energy guarantees that the final energy of the system
is the same as the initial energy.
 The work-energy principle is also a useful approach to the use of conservation of energy
in mechanics problem solving. It is particularly useful in cases where an object is brought
to rest as in a car crash or the normal stopping of an automobile.

 Kinetic energy is energy of motion. Objects that are moving, have kinetic energy (KE). If a
car crashes into a wall at 5 mph, it shouldn't do much damage to the car. But if it hits
the wall at 40 mph, the car will most likely be totaled. Kinetic energy is similar to
potential energy. The more the object weighs, and the faster it is moving, the more
kinetic energy it has. The formula for KE is: KE = 1/2*m*v2 where m is the mass and v is
the velocity.
 The kinetic energy increases with the velocity squared. This means that if a car is going
twice as fast, it has four times the energy. It may be noticed that the car accelerates
much faster from 0 mph to 20 mph than it does from 40 mph to 60 mph. Let's compare
how much kinetic energy is required at each of these speeds. At first glance, you might
say that in each case, the car is increasing its speed by 20 mph, and so the energy
required for each increase must be the same. But this is not so. We can calculate the
kinetic energy required to go from 0 mph to 20 mph by calculating the KE at 20 mph and
then subtracting the KE at 0 mph from that number. In this case, it would be 1/2*m*202
- 1/2*m*02. Because the second part of the equation is 0, the KE = 1/2*m*202, or 200
m. For the car going from 40 mph to 60 mph, the KE = 1/2*m*602 - 1/2*m*402; so KE =
1,800 m - 800 m, or 1000 m. Comparing the two results, we can see that it takes a KE of
1,000 m to go from 40 mph to 60 mph, whereas it only takes 200 m to go from 0 mph to
20 mph.
 There are a lot of other factors involved in determining a car's acceleration, such as
aerodynamic drag, which also increases with the velocity squared. Gear ratios
determine how much of the engine's power is available at a particular speed, and
traction is sometimes a limiting factor. So it's a lot more complicated than just doing a
kinetic energy calculation, but that calculation does help to explain the difference in
acceleration times.

ENGINE LOCATION
Front engine:
 The large mass of an engine at the front of the car gives the driver protection in the
event of a head on collision.
 Engine cooling is simpler to arrange and in addition the cornering ability of a vehicle
is normally better if the weight is concentrated at the front.
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 Figure 1.1. Location of engine in front engine vehicle.

 Advantages:
 Better axle load distribution
 Better road grip
 Comfort riding
 Better cooling
 Less noise (long exhaust pipe)
 Use a long engine

Rear engine:
 It increases the load on the rear driving wheels, giving them better grip of the road.
Most rear-engine layouts have been confined to comparatively small cars, because the
heavy engine at the rear has an adverse effect on the ‘handling’ of the car by making it
‘tail- heavy’.
 Also it takes up good deal of space that would be used on a front-engine car for carrying
luggage.
 Most of the space vacated by the engine at the front end can be used for luggage, but
this space is usually less than that available at the rear.

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 Figure 1.2. Location of engine in rear engine vehicle.

Central and mid-engine:

 These engine situations generally apply to sports cars because the engine sitting gives a
load distribution that achieves both good handling and maximum traction from the
driving wheels.
 These advantages, whilst of great importance for special cars, are outweighed in the
case of everyday cars by the fact that the engine takes up space that would normally be
occupied by passengers.
 The mid-engine layout shown combines the engine and transmission components in one
unit. The term mid-engine is used because the engine is mounted in front of rear axle
line.

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 Figure 1.3. Location of engine in different types of cars.

DECELERATION OF VEHICLE AND PASSENGER COMPARTMENT ON IMPACT

WITH STATIONARY AND MOVABLE OBSTACLE

It is important to study the deceleration inside passenger compartment to know the effect
of crash completely, so that the crash avoidance systems can be suitably designed. For example,
if the deceleration of the passenger after crash is very high, the air bag system and the seat belt
system has to be so designed that the activation time for them is reduced to a lower value.
Otherwise it may lead to injuries and fatalities.
Usually tests are conducted to know the deceleration behavior after the crash with
a stationary obstacle. The tests are conducted at the following speeds:
1. 15 mph (miles per hour)
2. 20 mph
3. 40 mph
4. 50 mph
15 mph test:
The following pictures show the body deformation and acceleration graph after crash.
The body deformation is less as the vehicle speed is low. The crash occurs at time 0 seconds.
From the graph, we can know that after the crash, deceleration occurs which is shown in the
negative (lower) portion. Its value is up to 20g. After some time the acceleration slowly comes to
zero (the car stops)

Figure 1.4. Deceleration characteristics in car after impact with stationary object (at 15 mph speed testing condition).

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20 mph test:
In the 20 mph test, the body deformation is more than 15 mph test. Moreover, the
acceleration has reduced to a further lower value (up to 35 g) in the negative direction. In this
case the maximum deceleration is obtained in 50 milli seconds whereas for 10 mph test it was 35
milli seconds. The rebound velocity for this case is1.7 mph whereas for 10 mph it is 1.3 mph.40
mph test: In the 40 mph test, we can see that the acceleration curve goes down (deceleration)
then suddenly goes up in the positive region (acceleration). This is due to the fact that, at 40
mph, the deformation is more and the accelerometer (sensor) mounting area has buckled and
resulted in an increase in acceleration value. The body deformation is also high such that the
accelerometer mounting area is also damaged. So, we have to carefully analyze the graph to
study the situation.

Figure 1.5. Deceleration characteristics in car after impact with stationary object (at 20 mph speed testing condition).

40 mph test:
In the 40 mph test, we can see that the acceleration curve goes down (deceleration) then
suddenly goes up in the positive region (acceleration). This is due to the fact that, at 40 mph, the
deformation is more and the accelerometer (sensor) mounting area has buckled and resulted in an
increase in acceleration value. The body deformation is also high such that the accelerometer
mounting area is also damaged. So, we have to carefully analyze the graph to study the situation.

Figure 1.6. Deceleration characteristics in car after impact with stationary object (at 40 mph speed testing condition).

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 50 mph test:
The body deformation is very high as the speed is more. The acceleration curve shows that the
maximum deceleration is around 35g and happens in time duration of 45 milli seconds. The
rebound velocity is 1.6 mph.

Figure 1.7. Deceleration characteristics in car after impact with stationary object (at 50 mph speed testing
condition). DECELERATION ON IMPACT WITH A MOVABLE OBSTACLE:

A movable obstacle can be another car or any other vehicle. Let us consider a car is impacting
with another car. We shall study for the two cars; one car which is impacting the second car, the
other car is which is being impacted. In this case the test is conducted at 40 mph.

Figure 1.8. Deceleration characteristics in car after impact with movable object (at 40 mph speed testing condition).

The impact velocity was 40.6 mph with a separation velocity of 18.0 mph for a total velocity
change of 22.6 mph. A maximum of 15g’s deceleration was achieved at about 50 milliseconds.
The total impact duration was approximately 195 milliseconds
83
Impacted vehicle:

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Figure 1.9. Deceleration characteristics in car after impact with movable object (at 18 mph speed testing condition).

The pre-impact velocity was 0.0 mph with a separation velocity of 22.8 for a total velocity
change of 22.8mph. A maximum of 16.5g’s acceleration was achieved at about 15 milliseconds.
The total impact duration was approximately 195 milliseconds.

CONCEPT OF CRUMBLE ZONE

 Crumple zones are designed to absorb the energy from the impact during a traffic
collision by controlled deformation.
 The crumple zone of an automobile is a structural feature designed to compress during
an accident to absorb energy from the impact. Typically, crumple zones are located in
the front part of the vehicle, in order to absorb the impact of a head-on collision, though
they may be found on other parts of the vehicle as well. Some racing cars use aluminum
or composite honeycomb to form an 'impact attenuator' for this purpose.
 It was an inventor Bela Barenyi who pioneered the idea that passengers were safer in a
vehicle that was designed to easily absorb the energy from an impact and keep that
energy away from the people inside the cabin. Barenyi devised a system of placing the
car's components in a certain configuration that kept the kinetic energy in the event of a
crash away from a bubble protecting the car's occupants.
 Mercedes obtained patent from Barenyi's invention way back in 1952 and the
technology was first introduced into production cars in 1959 in the Mercedes-Benz 220,
220 S and 220 SE models.

Auto safety has come a long way in the last few decades, and one of the most effective innovations
is the crumple zone. Also known as a crush zone, crumple zones are areas of a vehicle that are
designed to deform and crumple in a collision. This absorbs some of the energy of the impact,
preventing it from being transmitted to the occupants.

Of course, keeping people safe in auto accidents isn't as simple as making the whole vehicle
crumple. Engineers have to consider many factors in designing safer cars, including vehicle size and
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weight, frame stiffness and the stresses the car is likely to be subjected to in a crash. For example,
race cars
experience far more severe impacts than street cars, and SUVs often crash with more force than
small cars.

Function:
 Crumple zones work by managing crash energy, absorbing it within the outer sections of
the vehicle, rather than being directly transmitted to the occupants, while also
preventing intrusion into or deformation of the passenger cabin.
 This better protects car occupants against injury. This is achieved by controlled
weakening of sacrificial outer parts of the car, while strengthening and increasing the
rigidity of the inner part of the body of the car, making the passenger cabin into a 'safety
cell', by using more reinforcing beam sand higher strength steels. Volvo introduced the side
crumple zone; with the introduction of the SIPS (Side Impact Protection System) in the early
1990s.
 The purpose of crumple zones is to slow down the collision and to absorb energy. It is
like the difference between slamming someone into a wall headfirst (fracturing their
skull) and shoulder-first (bruising their flesh slightly) is that the arm, being softer, has
tens of times longer to slow its speed, yielding a little at a time, than the hard skull,
which isn't in contact with the wall until it has to deal with extremely high pressures.
 Seatbelts restrain the passenger so they don't fly through the windshield, and are in the
correct position for the airbag and also spread the loading of impact on the body. Seat
belts also absorb energy by being designed to stretch during an impact, so that there is
less speed differential between the passenger's body and their vehicle interior. In short:
A passenger whose body is decelerated more slowly due to the crumple zone (and other
devices) over a longer time, survives much more often than a passenger whose body
indirectly impacts a hard, undamaged metal car body which has come to a halt nearly
instantaneously.
 The final impact after a passenger's body hits the car interior, airbag or seat belts, is that
of the internal organs hitting the ribcage or skull. The force of this impact is the
mechanism through which car crashes cause disabling or life threatening injury. The
sequence of energy is dissipating and speed reducing technologies - crumple zone - seat
belt - airbags - padded interior, are designed to work together as system, to reduce the
force of this final impact.
 A common misconception about crumple zones is that they reduce safety by allowing
the vehicle's body to collapse, crushing the occupants. In fact, crumple zones are
typically located in front and behind of the main body (though side impact absorption
systems are starting to be introduced), of the car (which forms a rigid 'safety cell'),
compacting within the space of the engine compartment or boot/trunk.

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 The marked improvement over the past two decades in high speed crash test results
and real-life accidents also belies any such fears.
 Modern vehicles using what are commonly termed 'crumple zones' provide far superior
protection for their occupants in severe tests than older models, or SUVs that use a
separate chassis frame and have no crumple zones.

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SAFETY SANDWICH CONSTRUCTION:
 Sandwich panel constructions using metallic and polymeric honeycombs and foams
have been used for many years in the competition and high performance sectors of the
automotive industry, and there is considerable knowledge and confidence in their static,
dynamic and crashworthiness properties.
 Sandwich panels have only been used to produce extremely limited numbers of product
and have been essentially hand-worked.
 The potential advantages of polymer composites for automotive parts (high specific
strength and stiffness, corrosion resistance) are well known. Further benefits are
available
from the use of sandwich construction, in which a relatively stiff, strong skin is bonded
either side of a much thicker, lightweight core.
 Sandwich panels have been widely used for structural applications in the marine,
aerospace and performance automotive industries for several decades.
 Lightweight core materials have included balsa, polymer foams and metallic, paper or
polymer honeycombs. These have been used in various combinations with skins of
carbon, glass and/or aramid fiber-reinforced polymer, as well as aluminium.The
principle of sandwich construction is that bending loads are carried by the skins, while
the core transmits shear load.
 They enable large gains in structural efficiency, since the thickness (and hence flexural
rigidity) of panels can be increased without significant weight penalty.
 In high performance car construction, most sandwich panel elements are vacuum
bag/autoclave molded on a contact tool, usually in several stages (e.g. first skin; core to
skin bond; second skin).
 Although this permits complex shapes to be produced on low cost tooling, it is
necessarily a time consuming and labor intensive process.
 A high degree of cleanliness and sophisticated process control are required, and
inspection is notoriously difficult.
 Sandwich panels are also available as flat sheet, stock material.
 Hexcel Composites, for example, supply arrange of honeycomb cored sheets of varying
specifications which is widely used for building cladding, aircraft flooring, luggage bins
and bulkheads.
 The use of a stock material is attractive, since primary material quality and specification
becomes the responsibility of the supplier, not the manufacturer.
 Several techniques are well established for the shaping and assembly of structural
components from flat sandwich panel. Panels may be bent to required angles by
removing a defined strip of material from the inner skin, then folding and adhesively
bonding the joint.

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 Figure 1.10. Safety structures – Sandwich composite materials.

 For additional strength, reinforcing material can be added at the skin joints. It is
emphasized at this point that the process of shaping a panel requires no tooling,
and assembly can often be arranged so that parts are self-jigging.
 The panels can be machined with hand tools a major attraction of these techniques is
the potential they offer for computer control and automation.

Importance of ergonomics in automotive safety:

Ergonomics is the interaction between a person and the things they use. For example, the products
usability and the comfort level. The things to keep in mind are that many demographics are now
using vehicles such as women driving SUVs, elderly people, differently abled or special needs
people who need to drive vehicles. There are mainly five aspects of ergonomics - safety, comfort,
ease of use, productivity and aesthetics. While spending for aesthetics is a stretch, spending for
safety is something that customers don't have any qualms about. It is the one aspect that no one
wants to compromise on. Usually there are standard features for safety such as airbags in every
car. However, extra care needs to be taken if optimum safety is to be ensured.

TEXT / REFERENCE BOOKS

1. Powloski.J - “Vehicle Body Engineering” - Business books limited, London - 1969.
2. Ronald.K.Jurgen - “Automotive Electronics Handbook” - Second edition- McGraw-Hill Inc., -
1999.
3. Johnson, W., and Mamalis, A.G., "Crashworthiness of Vehicles, MEP, London, 1995
4. Bosch - “Automotive Handbook” - 5th edition - SAE publication - 2000.

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Further Reading:
1. George A. Peters and Barbara J. Peters, Automotive Vehicle Safety, Taylor & Francis,
2003.
2. G.S. Daehn, Sustainable design and manufacture of lightweight vehicle structures, in
Alternative Fuels and Advanced Vehicle Technologies for Improved Environmental
Performance, 2014. https://doi.org/10.1533/9780857097422.2.433.
3. Paul M. Leonardi, Car Crashes without Cars, THE MIT Press, Massachusetts Institute of
Technology, 2012.
4. Ulrich Seiffert and Lothar Wech, Automotive Safety Handbook, Second Edition, Society
of Automotive Engineers, SAE International, 2003.
5. Ing. Konrad Reif Ed, Fundamentals of Automotive and Engine Technology, Bosh
Professional Automotive Information, Springer Vieweg, 2014.
6. Hermann Winner, Stephan Hakuli, Felix Lotz, Christina Singer Eds., Handbook of Driver
Assistance Systems, Springer Reference, 2016.
7. Ulrich Seiffert, Mark Gonter, Integrated Automotive Safety Handbook, SAE
International, 2014. doi:10.427/R-407.

Active safety: driving safety, conditional safety, perceptibility safety, operating

safety Passive safety: exterior safety, interior safety,
Deformation behavior of vehicle body
Speed and acceleration characteristics of passenger compartment on impact.

Passenger safety occupies a prime spot in the automobile sector today. Stakeholders across
the automobile value chain acknowledge the importance of passenger/occupant safety and are
constantly upgrading their offerings to provide fail safe safety technologies that will protect
passengers and pedestrians. Proactive policy implementation and consumer awareness has played a
key role in making automotive safety systems popular. However the penetration of these lifesaving
technologies differs from country to country. Economically developed countries tend to have a high
penetration of these technologies across various passenger and commercial vehicle segments.
Traditionally Automobile Safety Systems can be classified in to two segments, namely Active
Safety Systems and Passive Safety Systems.

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 Figure 2.1. Distribution of automotive safety systems in various countries.

Active Safety Systems as the term suggests play a preventive role in mitigating crashes and
accidents by providing advance warning or by providing the driver with additional assistance in
steering/controlling the vehicle. Head-Up Display (HUD), Anti-Lock Braking Systems (ABS),
Electronic Stability Control (ESC), Tire Pressure Monitoring System (TPMS), Lane Departure
Warning System (LDWS), Adaptive Cruise Control (ACC), Driver Monitoring System (DMS),
Blind Spot Detection (BSD) and Night Vision System (NVS) are common Active Safety Systems.
Passive Safety Systems play a role in limiting/containing the damage/injuries caused to driver,
passengers and pedestrians in the event of a crash/accident. Airbags, Seatbelts, Whiplash
Protection System etc. are common Passive Safety Systems deployed in vehicles these days. An
emerging trend witnessed in the global automotive safety system market is the increasing demand

91
from the countries like India, China, Russia and Brazil. Since the market for the safety systems
like Airbags and ABS in developed economies is maturing and becoming saturated, OEMs and
suppliers are focusing on increase demand from emerging markets. The demand is becoming
higher in emerging markets primarily because of the improving road safety standards/supporting
legislation and consumer awareness. Rapidly increasing vehicle population in emerging markets
such as China, Thailand, Brazil and India is also driving up the risk of road fatalities and
supporting demand for safety systems in passenger and commercial vehicles. Further, programmes
like New Car Assessment Programe (NCAP) a government car safety evaluation programme
which provides ratings, based on the safety performance of cars have become a catalyst for
encouraging significant safety improvements initiatives from original equipment manufacturers,
that drive consumer confidence and hence demand for Active and Passive Safety Systems.

ACTIVE SAFETY:
 Active safety systems help prevent accidents and thus make a preventive contribution to safety
in road traffic.
 Active safety systems are designed to help you avoid a crash in the first place.
 One example of an active driving safety system is the Antilock Braking System (ABS) with
Electronic Stability Program (ESP) from Bosch, which stabilizes the vehicle even in critical braking
situations and maintains steerability in the process.
Driving safety
 It is the result of a harmonious chassis and suspension design with regard to wheel suspension,
springing, steering and braking, and is reflected in optimum dynamic vehicle behavior.
Conditional safety
 It results from keeping the physiological stress that the vehicle occupants are subjected
to by vibration, noise, and climatic conditions down to as low a level as possible. It is a
significant factor in reducing the possibility of miss actions in traffic.
 Vibrations within a frequency range of 1 to 25 Hz (stuttering, shaking, etc.) induced by
wheels and drive components reach the occupants of the vehicle via the body, seats and
steering wheel. The effect of these vibrations is more or less pronounced, depending
upon their direction, amplitude and duration.
 Noises as acoustical disturbances in and around the vehicle can come from internal
sources (engine, transmission, prop shafts, axles) or external sources (tire/road noises,
wind noises), and are transmitted through the air or the vehicle body.
 The sound pressure level is measured in dB(A) (see Motor-vehicle noise measurements
and limits).Noise reduction measures are concerned on the one hand with the
development of quiet- running components and the insulation of noise sources (e.g.,
engine encapsulation), and on the other hand with noise damping by means of
insulating or anti-noise materials.
 Climatic conditions inside the vehicle are primarily influenced by air temperature, air
humidity, rate of airflow through the passenger compartment and air pressure (see
Environmental stresses for additional information).
Perceptibility safety
 Measures which increase perceptibility safety are concentrated
 Lighting equipment (see Lighting),
 Acoustic warning devices (see Acoustic signaling devices),
 Direct and indirect view (see Main dimensions) (Driver's view: The angle of
obscuration caused by the A-pillars for both of the driver's eyes binocular must not
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 be more than 6 degrees).

Operating safety
Low driver stress, and thus a high degree of driving safety, requires
optimum design of the driver surroundings with regard to ease of operation
of the vehicle controls.

Table 2.1. Active Safety Systems.

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Active Safety Features:
Active safety features are designed to keep in full control of the vehicle at all times using
advanced technologies. These technologies attempt to avoid accidents in the first place, and they
are always on, alerting commuters. Thus, these safety features are always “active.”
Here are some of the features they include:
Active Brakes – These brakes help make driving easier in a number of different ways by applying
added braking pressure when emergency braking, automatically drying themselves when it’s wet,
and decreasing erratic driving.
Dynamic Stability Control – Using advanced sensors and the strategic delivery of torque and
brake pressure to the wheels, this system is able to help you stay stable on the road.
Head-Up Display – Keep your eyes on the road to avoid a collision while still getting access to
important information like your speed, navigation directions, and radio.
Cornering Brake Control – When you’re taking a corner at speed, this system applies the brakes
automatically to help you stay in control.
Adaptive Cruise Control – This feature is able to automatically maintain a safe distance between
your car and the one in front of you.

PASSIVE SAFETY:

 A passive safety system helps to protect from injury if a crash is unavoidable.It refersto
components of the vehicle (primarily airbags, seatbelts and the physical structure of the vehicle)
that help to protect occupants during a crash
 Passive safety systems serve to protect the occupants against serious or even fatalinjuries.
 An example of passive safety is the airbags, which protect the occupantsfollowing an
unavoidable impact.
Exterior safety
The term "exterior safety" covers all vehicle-related measures which are designed to
minimize the severity of injury to pedestrians and bicycle and motorcycle riders struck by the
vehicle in an accident. Those factors which determine exterior safety are:
 Vehicle-body deformation behavior,
 Exterior vehicle body shape.

The primary objective is to design the vehicle such that its exterior design minimizes the
consequences of a primary collision (a collision involving persons outside the vehicle and the
vehicle itself).The most severe injuries are sustained by passengers who are hit by the front of the
vehicle, whereby the course of the accident greatly depends upon body size. The consequences of
collisions involving two-wheeled vehicles and passenger cars can only be slightly ameliorated by
passenger-car design due to the two-wheeled vehicle's often considerable inherent energy
component, its high seat position and the wide dispersion of contact points. Those design features
which can be incorporated into the passenger car are, for example:
 Movable front lamps
 Recessed windshields wipers,
 Recessed drip rails,
 Recessed door handles.
Interior safety

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 The term "interior safety" covers vehicle measures whose purpose is to minimize the
accelerations and forces acting on the vehicle occupants in the event of an accident, to provide
sufficient survival space, and to ensure the operability of those vehicle components critical to the
removal of passengers from the vehicle after the accident has occurred. The determining factors
for passenger safety are:
 Deformation behavior (vehicle body),
 Passenger-compartment strength, size of the survival space during and after impact,
 Restraint systems,
 Impact areas (vehicle interior),
 Steering system,
 Occupant extrication,
 Fire protection.

Laws which regulate interior safety (frontal impact) are:

 Protection of vehicle occupants in the event of an accident, in particular restraint systems
 Windshield mounting
 Penetration of the windshield by vehicle body components
 Parcel-shelf and compartment lids

Rating-Tests:
 New-Car Assessment Program (NCAP, USA, Europe, Japan, Australia),
 IIHS (USA, insurance test),
 ADAC, ams, AUTO-BILD.

Passive Safety Features:

Passive safety features are designed to mitigate the impact of a collision when it does occur. So, they
remain passive unless called upon.
Passive features on MINI cars include:
Smart Airbags – New MINI vehicles come with up to eight smart airbags.
Crash Sensor System – This feature automatically unlocks the doors, turns on the hazard lights,
and cuts the fuel pump when the airbags go off.
Breakaway Engine – This feature helps the engine and gearbox absorb as much of the impact as
possible in case of a forward collision.
Rollover Protection Bar – This mounted safety bar can deploy in just seconds to provide added
protection if the vehicle rolls over.
Engine Immobilizer – This system automatically immobilizes the engine without the key.

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Table 2.2. Passive Safety Systems.

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 Head up display:
The automotive HUD finds application in the majority of the passenger car segments. Given the
increasing adoption of HUD in the automotive sector, it has become a standard feature for various
models in the luxury car segment. Additionally, the increasing demand for comfort and safety has
compelled automakers to incorporate this feature in premium and mid segment models as well. The
market in growing regions such as Asia-Pacific, and North America indicate promising growth
potential for the automotive HUD market. The Asia-Pacific automotive market in particular
presents high-growth opportunities; the region includes Japan, China, and India, with the latter two
having huge production capabilities. The European HUD market is primarily driven by the growing
awareness regarding driver safety and convenience. Europe has many luxury/premium car
manufacturers. Major high-end car OEMs such as Audi AG (Germany), BMW (Germany),
Mercedes-Benz (Germany), Bentley Motors (UK), Maserati (Italy), Ferrari (Italy), and Bugatti
Automobiles (France) have their headquarters in Europe. The automotive HUD comes as standard
safety feature in the majority of European automobiles. The region therefore has a wide customer
base for this technology.
Windshield head up display technology and combiner head UP display technology:
The windshield head up display projects a virtual image with the necessary information needed by
the driver. This information is projected in accordance with the drivers eye gaze. In this technology
type, the windshield of the car plays an important role as there are chances that the image produced
by the device can be distorted. The conventional HUD uses TFT displays which projects images on
the windscreen. With the advancement in technology there have been improvements in the display
technology. One of the differentiating factors between the two types of HUDs is the space
requirement and image resolution. The Combiner HUD type has a smaller screen which displays the
necessary information but lacks the picture quality as compared to the other type. The Combiner
HUD has an adjustable positioning system which enables the driver to adjust the screen according
to their convenience.

Augmented Reality head up display technology:

Augmented reality (AR) is an upcoming trend in the head-up display market. Augmented HUD is a
real time technology which enhances the safety and driving experience. Augmented reality-based
HUD technology provides full-colour advanced driver assistance system (ADAS) including lane
departure warning system and advanced driving information. The AR-HUD sense the exterior
environment of the vehicle, analyses this information and virtually display the traffic condition. For
example, if the driver has set a destination on the navigation system, the AR-HUD projects a virtual
route that is to be followed. It also detects the distance between itself and the vehicle in front and
alerts the driver. The differentiating factor for AR-HUD is that it projects information which
appears to be part of the driving situation itself.

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DEFORMATION BEHAVIOR OF VEHICLEBODY
Due to the frequency of frontal collisions, an important role is played by the legally
stipulated frontal impact test in which a vehicle is driven at a speed of 48.3 km/h (30 mph) into a
rigid barrier which is either perpendicular or inclined at an angle of up to 30° relative to the
longitudinal axis of the car.

Figure 2.2. Distribution of various types of impacts in car accidents.

 Because 50 % of all frontal collisions in right-hand traffic primarily involve the left-hand
half of the front of the vehicle, manufacturers worldwide conduct left asymmetrical
front impact tests on LHD vehicles covering 30 ... 50 % of the vehicle width. Distribution
of accidents by type of collision, Symbolized by test methods yielding equal results in a
frontal collision, kinetic energy is absorbed through deformation of the bumper, the
front of the vehicle, and in severe cases the forward section of the passenger
compartment (dash area). Axles, wheels (rims) and the engine limit the deformable
length. Adequate deformation lengths and displaceable vehicle aggregates are
necessary, however, in order to minimize passenger-compartment acceleration.
 Depending upon vehicle design (body shape, type of drive and engine position),
vehicle mass and size, a frontal impact with a barrier at approx. 50 km/h results in
permanent deformation in the forward area of 0.4 0.7 m. Damage to the passenger
compartment should be minimized. These concerns primarily dash area (displacement
of steering system, instrument panel, pedals, toe- panel intrusion), underbody
(lowering or tilting of seats), the side structure (ability to open the doors after an
accident).
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  Acceleration measurements and evaluations of high-speed films enable deformation
behavior to be analyzed precisely. Dummies of various sizes are used to simulate vehicle
occupants and provide acceleration figures for head and chest as well as forces acting on
thighs. Head acceleration values are used to determine the head injury criterion (HIC).
The comparison of measured values supplied by the dummies with the permissible limit
values as per FMVSS 208 (HIC: 1000, chest acceleration: 60 g/3 ms, upper leg force: 10
kN) are only limited in their applicability to the human being.
 The side impact, as the next most frequent type of accident, places a high risk of injury
on the vehicle occupants due to the limited energy absorbing capability of trim and
structural components, and the resulting high degree of vehicle interior deformation.
The risk of injury is largely influenced by the structural strength of the side of the vehicle
(pillar/door joints, top/bottom pillar points), load-carrying capacity of floor cross-
members and seats, as well as the design of inside door panels (FMVSS 214, ECE R95,
Euro-NCAP, US- SINCAP).In the rear impact test, deformation of the vehicle interior must
be minor at most.
 It should still be possible to open the doors, the edge of the trunk lid should not
penetrate the rear window and enter the vehicle interior, and fuel-system integrity must
be preserved (FMVSS 301).Roof structures are investigated by means of rollover tests
and quasi-static car-roof crush tests(FMVSS 216).
 In addition, at least one manufacturer subjects his vehicles to the inverted vehicle drop
test in order to test the dimensional stability of the roof structure (survival space) under
extreme conditions (the vehicle falls from a height of 0.5 m onto the left front corner of
its roof).

Figure 2.3. Acceleration, Speed and distance travelled during a car accident.

Acceleration, speed and distance traveled, of a passenger compartment when impacting a barrier
impacting a barrier at 50 km/h.

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SPEED AND ACCELERATION CHARACTERISTICS OF VEHICLE BODY:

Velocity graph for 15 mph barrier test:

Figure 2.4. Velocity graph during a barrier test conducted at 15 mph.

Velocity graph for 20 mph barrier test:

Figure 2.5. Velocity graph during a barrier test conducted at 20 mph.

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Velocity graph for 40 mph barrier test:

Figure 2.6. Velocity graph during a barrier test conducted at 40 mph.

Velocity graph for 50 mph barrier test:

Figure 2.7. Velocity graph during a barrier test conducted at 50 mph.

 All the graphs show the reduction in velocity (speed) of passenger compartment on
impact. For 15 mph and20 mph barrier test, we can see that the velocity comes to zero,
crosses zero line, stays in the negative region afterwards.
 Velocity in negative region means that the car is moving in opposite direction (i. e.) after
the collision it moves back. But for 40 mph test, the velocity comes close to zero and lies
in the positive region. It means that after the impact, the car does not bounce back
much, because most of the energy of the crash is taken by deforming the body metal.
 But in 15 mph and 20 mph tests, as the speed is low, the kinetic energy to deform the
body metal is also less and hence the body metal does not deform and stands rigid. So,

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 the car bounces back and velocity is slightly in the negative region.

TEXT / REFERENCE BOOKS

1. Powloski.J - “Vehicle Body Engineering” - Business books limited, London - 1969.
2. Ronald.K.Jurgen - “Automotive Electronics Handbook” - Second edition- McGraw-Hill Inc., -
1999.
3. Johnson, W., and Mamalis, A.G., "Crashworthiness of Vehicles, MEP, London, 1995
4. Bosch - “Automotive Handbook” - 5th edition - SAE publication - 2000.

Further Reading:
1. George A. Peters and Barbara J. Peters, Automotive Vehicle Safety, Taylor & Francis,
2003.
2. G.S. Daehn, Sustainable design and manufacture of lightweight vehicle structures, in
Alternative Fuels and Advanced Vehicle Technologies for Improved Environmental
Performance, 2014. https://doi.org/10.1533/9780857097422.2.433.
3. Paul M. Leonardi, Car Crashes without Cars, THE MIT Press, Massachusetts Institute of
Technology, 2012.
4. Ulrich Seiffert and Lothar Wech, Automotive Safety Handbook, Second Edition, Society
of Automotive Engineers, SAE International, 2003.
5. Ing. Konrad Reif Ed, Fundamentals of Automotive and Engine Technology, Bosh
Professional Automotive Information, Springer Vieweg, 2014.
6. Hermann Winner, Stephan Hakuli, Felix Lotz, Christina Singer Eds., Handbook of Driver
Assistance Systems, Springer Reference, 2016.
7. Ulrich Seiffert, Mark Gonter, Integrated Automotive Safety Handbook, SAE
International, 2014. doi:10.427/R-407.

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 COLLISION WARNING AND AVOIDANCE

 COLLISION WARNING SYSTEM

 CAUSES OF REAR END COLLISION
 FRONTAL OBJECT DETECTION
 REAR VEHICLE OBJECT DETECTION SYSTEM
 OBJECT DETECTION SYSTEM WITH BRAKING SYSTEM INTERACTIONS.

1. COLLISION WARNING SYSTEM

Collision Warning with Auto Brake is an active safety system that helps the driver to
avoid or mitigate rear-end collisions.
It uses forward-looking sensors to detect obstacles ahead of the vehicle.
When a high risk for a rear-end collision is detected the system helps the driver by
providing a warning and brake support.
If the driver does not react in time and a collision is judged to be unavoidable, the
systemwill automatically brake the vehicle.
This may not avoid the accident, but the consequences can be reduced.
This system is introduced in two steps. The first generation, called Collision Warning
with Brake Support, is currently on the market in the new Volvo S80 allowing activation
on vehicles that are moving or have been detected as moving. The second generation,
called Collision Warning with Auto Brake
Collision Warning with Auto Brake where the area in front of the vehicle is continuously
monitored with the help of a long-range radar and a forward-sensing wide-angle camera
fitted in front of the interior rear-view mirror.
A warning and brake support will be provided for collisions with other vehicles, both
moving and stationary.
If the driver does not intervene in spite of the warning and the possible collision is judged
to be unavoidable; intervention braking is automatically applied to slow down the car.
This aims at reducing impact speeds and thus the risk for consequences.

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Figure 4.1. Schematic of collision warning system.

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Components of collision warning system:
 Sensor System
Information about the traffic situation in front of the host vehicle is obtained from
two sensors:- A 77-GHz mechanically-scanning forward looking radar, mounted
in the vehicles grille, which measures target information such as range, range rate
and angle in front of the vehicle in a 15 degree field-of-view.
A 640*480 pixel black and white progressive scan CMOS camera, mounted
behind the windscreen, which is used for classifying the objects, e.g. as vehicles,
in a 48-degree field-overview. Since the camera is used for reporting both vision
objects and lane markings, the field of view was chosen to work for both.

Figure 4.2. Collision warning system in vehicles.

 Collision Warning
The Collision Warning (CW) function is targeting to avoid or mitigate collisions
by means of warning the driver ahead of a possible collision.
The system requires high usability, low number of nuisance alarms and an
efficient Human Machine Interface (HMI).
The Collision Warning system should provide a relative late warning in order to
reduce nuisance alarms and to reduce the possible misuse where an early warning
system may build a trust that is falsely interpreted by the driver to allow for
execution of non-driving tasks. The activation of the Collision Warning will
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 therefore approximately occur when the driving situation is considered to be
unpleasant.
However, it shall allow the driver to brake to avoid or mitigate an accident
provided the following distance was initially longer than the warning distance.

Functions:
Threat Assessment
 The aim of the threat assessment is to understand if the information
fromthe forward sensing system shows that there is a risk for collision
 The first step is to approve a lead vehicle as staying in the forward path
within a given time to collision utilizing intra-vehicle and yaw-rate
information.
 Given an approved lead vehicle a second step calculates a total warning
distance, i.e. the predicted distance required for avoiding a collision.
 The total warning distance base calculation is derived from a sum of three
distinct distance calculations.
 The first is the driver reaction distance which is obtained from the
predicted driver reaction time multiplied by vehicle speed.
 The second is the system reaction distance which is obtained from the
system reaction time multiplied by vehicle speed.
 The third is the braking distance to avoid impact using the current
physical states of the lead vehicle and the host vehicle using the constant
acceleration model for the behavior of the host and the target vehicle
closely mimicking the CAMP late warning algorithm.
 The sum of above provides a total warning distance.
 If the distance to the forward vehicle becomes lower than the total
warning distance a warning is to be issued.

Collision Warning HMI

 An efficient HMI(Human Machine Interface) for a warning system is
characterized by a low driver reaction time, as this is crucial for improving
the possibility for the driver to mitigate or even avoid a collision.
 An efficient HMI puts requirements on low false and nuisance alarm
rates, since there is a risk for overexposure that may lead to drivers
deactivating the system.
 The warning interface is a dual modality warning incorporating visual and
audible channels.
 The visual warning is a flashing red horizontal line located in the lower
part of the windshield in the forward direction of the driver.
 The sound consists of tone burst with harmonics content.
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  When the audible warning is active the sound system is muted. The
Collision Warning can be turned off by a main switch.
 The system includes a warning distance setting using three levels. The
levels have been defined by balancing driver behavior in late brake
situations versus normal driving behavior.
 The warning distance settings are differentiated by the deceleration level
used in the different settings the predicted brake ability by the driver.
 They also reduce warnings in normal driving situations to different levels.

Figure 4.3. Collision Warning head-up display

Driver Over ride:

 The objective of the driver override function is to inhibit a brake intervention
when the driver has the situation under control. However, this is difficult or even
impossible to measure and therefore driver inputs as steering and braking
activities are considered instead, as these are the natural countermeasures in a
collision event.
 The release of the accelerator pedal is considered, as this indicates that any
further acceleration is undesired, and it can be assumed that the driver is
thereby acknowledging a collision risk.
 Since the level of action that is required to activate a steering or brake override
depends on the driver and on the traffic situation, the decision threshold is
empirically determined through extensive testing in real life traffic situations
with a large number of drivers.

Auto Brake
 It is beneficial to the driver to get support in the upcoming collision event. This
can be achieved by reducing the collision energy by optimizing driver initiated
braking or through automatically putting on the brakes prior to the collision
event.

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  When providing autonomous interventions that override or complement the
driver’s actions, one has to ensure that customer satisfaction is not negatively
affected by false interventions.
 Customer acceptance is crucial in order to increase take rates and thus to
increase the overall real- life safety benefit of the system. It is therefore
necessary to implement a decision making strategy that reduces the amount of
false interventions while not missing collision events where the driver needs
support. Therefore, an intervention decision should be based on two main
information categories: traffic situation data and driver actions. The traffic
situation data is used to quantify the risk for a collision event, in other words a
threat assessment is performed.
 This assessment will never be perfect as sensor information is usually a subset of
the totally available information and mostly affected by latencies. So, a collision
may appear to be unavoidable but is in reality avoidable. Hence, a driver that
takes distinct steering and/or braking action is judged to be in control of the
situation and should be trusted. The driver override function is to detect these
distinct driver actions.
 As soon as the support system has performed the threat assessment and driver
override detection, the outcome can be weighted by the brake intervention
strategy and a decision on an autonomous brake intervention can be taken
Functions of collision warning:
System functionality:
 Alerting the driver
 Braking control
 Restricted steering Driver functionality:
 Changing lanes
 Turning the system on and off
 Approaching another vehicle or Non
vehicle obstacle

2. REAR-IMPACT COLLISION WARNING SYSTEM (RICWS):

1. Common factors that contribute to rear-end collisions include by driver inattention or

distraction, tailgating, panic stops, and reduced traction due to weather or worn
pavement.
2. Rear impact crashes are the most frequent type of bus accidents.
3. Transit buses are particularly susceptible to rear impact collisions because of their
frequent stops, which often occur in traffic lanes.
4. The majorities of bus collisions occur while the bus is decelerating or stopped.

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 5. The preponderance of crashes occurs with buses stopped during daylight hours, in good
weather conditions, while traversing a straight path, and with the striking vehicle
attempting no avoidance or corrective action.
6. Rear-end collisions are common accident scenarios and a common cause of these accidents is
driver distraction and thus not reacting in time.

3. FRONTAL OBJECT DETECTION

Figure 4.4. System overview of frontal object detection

Figure 4.5. Schematic of frontal object detection system

SYSTEM OVERVIEW
 The Sensor system has two cameras that can detect vehicles in the medium and far range are installed
by the side of a rear-view mirror and at the ceiling above the back seat and the two sonar sensors that
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 can measure the distance in the near range are installed at the front and rearbumpers.
 Because the environment of the vehicle changes relatively fast as the speed ofa ego-vehicle is high,
we acquire 2 images of 1 field with 640×240 for avoiding the motion flow and use 320×240 image by
sub- sampling and acquire 2 signals of sonar sensors successively.

Determination Of The Day And Night Times

 The environment of a moving vehicle greatly varies, it is difficult to detect vehicles
using a single feature or pre-established vehicle templates.
 Various features or templates can be used for various environments, and by
applying the appropriate algorithm to the current environment the day or night
time can be determined.

Vehicle Detection in the Day Time

 The detection system in the day time consists of 4 parts, the preprocessing module
working on the input raw image, the vehicle candidate extraction module by a
shadow region and a template, the validation module by a prior knowledge, and the
fusion module for fusing sonar and image data.
1) Preprocessing:
2) Vehicle Candidate Extraction:
3) Vehicle Candidate Validation
4) Vehicle Detection Using Sonar Sensors

Figure 4.8. Vehicle Candidates Extraction

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 Figure 4.9.The symmetry rate and edge angle map

Figure 4.10. Vehicle detection at near distance

4. REAR VEHICLE OBJECT DETECTION SYSTEM

 Rear object detection systems monitor a specific area behind a commercial motor
vehicle, detect objects, and provide warnings to drivers when they are approaching an
object behind the vehicle while in reverse. These systems assist the driver in avoiding
collisions during backing or parking maneuvers.
 Rear object detection systems detect moving and stationary objects located within a
specific area behind a commercial motor vehicle while it is backing up. Currently
available systems can detect objects within a range of approximately 10 to 20 feet
behind a vehicle.
 They can be integrated with other sensors, such as side object detection sensors to
cover other blind spot areas around a vehicle.
 Audible and/or visual distance-based alerts that vary depending upon the closeness of
the vehicle to an obstacle are the types of warnings that can be provided to a driver
through a processing and/or display unit in the cab.
 The sensor units located on the back of the vehicle can consist of different types of
detection technology, such as radar or sonar.
 Ultrasonic technology or sonar (Sound Navigation And Ranging) determines the range
of objects by emitting a transmitter pulse of ultrasonic energy.
o The resultant echo is detected by a receiver as it is reflected from the detected
object.
o The emitter is a membrane that transforms mechanical energy into a chirp
(inaudible sound wave) and sends this sound out toward the target area.
o When the sound encounters an object, it is reflected back to the receiver circuit
that is tuned to the frequency of the emitter, which then transfers the data to a
driver display unit.
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 Radar (Radio Detection and Ranging) technology is also used for rear object detection
systems. Radar typically operates in the ultra-high-frequency or microwave range of the
radio- frequency spectrum.
o These radio frequency waves are transmitted from the vehicle at defined
intervals within a specific coverage area.
o The sensor collects echoes from electromagnetic waves that bounce off objects
behind the vehicle. These echoes are sent to a signal processing unit and
communicated to a driver interface.
o Some processing units utilize algorithms for object detection, object tracking,
and angle measurement to provide specific distance information.
Rear object detection systems provide audible and/or visual alerts to warn drivers when
objects are detected. Some systems indicate the vehicle's distance from a detected object.
For example, the driver interface may consist of a graphical or digital visual display that
shows the distance from the vehicle to a specific object. Other visual alerts could consist
of a series of lights which change color or light up as objects are detected. These visual
alerts can be used in combination with audible alerts that vary in tone and frequency as
the vehicle moves closer to an object.
Rear object detection systems can be activated manually when needed or automatically
for continuous operation. Some rear object detection systems are connected directly to the
vehicle's backup lights, which activate automatically when the vehicle is shifted into
reverse. Other systems are activated when the key is put into the ignition or the vehicle is
put into operation. When the systems are activated, their operation is "hands-free," and
the driver can focus on safely operating the vehicle.

TEXT / REFERENCE BOOKS

1. Powloski.J - “Vehicle Body Engineering” - Business books limited, London - 1969.
2. Ronald.K.Jurgen - “Automotive Electronics Handbook” - Second edition- McGraw-Hill Inc., -
1999.
3. Johnson, W., and Mamalis, A.G., "Crashworthiness of Vehicles, MEP, London, 1995
4. Bosch - “Automotive Handbook” - 5th edition - SAE publication - 2000.

Further Reading:
1. George A. Peters and Barbara J. Peters, Automotive Vehicle Safety, Taylor & Francis,
2003.
2. G.S. Daehn, Sustainable design and manufacture of lightweight vehicle structures, in
Alternative Fuels and Advanced Vehicle Technologies for Improved Environmental
112
 Performance, 2014. https://doi.org/10.1533/9780857097422.2.433.
3. Paul M. Leonardi, Car Crashes without Cars, THE MIT Press, Massachusetts Institute of
Technology, 2012.
4. Ulrich Seiffert and Lothar Wech, Automotive Safety Handbook, Second Edition, Society
of Automotive Engineers, SAE International, 2003.
5. Ing. Konrad Reif Ed, Fundamentals of Automotive and Engine Technology, Bosh
Professional Automotive Information, Springer Vieweg, 2014.
6. Hermann Winner, Stephan Hakuli, Felix Lotz, Christina Singer Eds., Handbook of Driver
Assistance Systems, Springer Reference, 2016.
7. Ulrich Seiffert, Mark Gonter, Integrated Automotive Safety Handbook, SAE
International, 2014. doi:10.427/R-407.

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