Date 9th / Jan/2025

Unit 3 of the syllabus Traffic Engineering

• 3E’s of, traffic characteristics,
• Surveys, volume,speed,parking etc
• Intersection-types,
• layouts,
• design principles,
• Urban traffic, parking, lighting,
• Accidents,
• Traffic control Devices-marking, Signs, Signals, Regulations Motor
Vehicle Act and Rules
Transportation Systems and their Function
• What is a system ?
• a set of things working together as parts of a mechanism or an
interconnecting network
• a set of principles or procedures according to which something is done; an
organized scheme or method.

• Transportation systems are a major component of the any economy

and have an enormous impact on the shape of the society and the
efficiency of the economy
Transportation Systems and their Function
• Transportation planners and traffic engineers attempt to provide
capacity for observed or predicted travel demand by building
Transportation systems.
• By Improving a transportation system
• making it and the nearby lands more accessible and,
• therefore, more attractive for development.

FOR ALL ABOVE THE TRANSPORTATION ENGINEER NEEDS TO ESTABLISH

DEMAND THER NEED FORCAST THE VOLUME POTIENTIAL USERS
Major Elements of Transportation System
• Mobility planning
• Traffic engineering
• Pavement design
• Pavement maintenance
• Transportation economics
Traffic engineering definition
• Traffic engineering is that phase of transportation engineering which
deals with the planning, geometric design and traffic operations of
roads, streets, and highways, their networks, terminals, abutting lands,
and relationships with other modes of transportation.
(learn I may ask for 2 marks)

• By the very definition it is clear that traffic is a multi disciplinary area

• Traffic engineering involves a variety of engineering and management
skills-including planning, management, design, construction,
operation, control, maintenance, and system optimization.
• traffic engineer’s work is a most visible part of the public
infrastructure, it is a field that also involves policies, law , law
enforcement at virtually every level of government.
Traffic engineering
• Traffic engineering covers a broad range of engineering applications with a
common focus:
• the nation’s system of highways and streets. Often defined as the nation’s
“lifeblood circulation system,”
• this important part of the national infrastructure supports the vast majority
of inter- and intra-city movement of both people and
goods.
• Traffic engineering involves a variety of engineering and management skills-
including planning, management, design, construction, operation, control,
maintenance, and system optimization.
The objective of traffic engineering
• The Primary Objective Expect a question on this slide

• Safety
Other objectives are
• Speed
• Comfort (providing physical ease and relaxation.)
• Convenience (The definition of convenience is the state of being able to do
something easily with little effort and no hindrances)
• Economy (careful management of available resources.)
• Environmental compatibility (Harmony with the environment is a complex
issue that has become more important over time )
Nature of traffic engineering
• Most of these are self-evident desires of the traveler.
• We want our trips to be
• fast,
• comfortable,
• convenient,
• cheap, and
• in harmony with the environment.
• All of these objectives are also relative and must be balanced against
each other and against the primary objective of safety.
Nature of Traffic engineering
• While speed of travel is much to be desired, it is limited by
• Transportation technology, (Petrol , diesel, electrical, atomic)
• Human characteristics (Weight, biological limitations, etc)
• Comfort and convenience are generic terms and mean different things to different
people.
• Comfort involves the physical characteristics of vehicles and roadways, and is
influenced by our perception of safety.
• Convenience relates more to the ease with which trips are made and the ability of
transport systems to accommodate all of our travel needs at appropriate
times.
• Economy is also relative
Elements of Traffic Engineering
• Traffic studies and characteristics
• Demand estimation
• Performance evaluation
• Facility design / planning
• Traffic control
• Traffic operations
• Transportation systems management
• Economic studies
• Financial studies
• Facility augmentation
• Integration of intelligent transportation system technologies
How to locate a facility?
• What is a Transportation facility?
• How do we locate one?
• Is there a demand?
• If so we supply?
• What do we supply?
• Decide : connectivity is needed between two land
masses
• Size of connectivity : Single lane road or six lane road or
a fly over or sky bus or local train of just a bus station or
air connectivity

• MOST IMPORTANT :: Where to locate a facility

• Like a bus terminal / air port / rail station /port
 Origin and destination studies
• Origin and destination determines the pattern of
travel of people
• It is an important tool for forecasting future demand
and performance of a transportation system,
• It was developed for evaluating large-scale
infrastructure projects
• It helps in deciding the location of a facility
 Origin and destination studies
• It helps in sufficiency studies
• It helps in socio-economics studies
• Deciding construction priorities and economic
justification of a decision
• Developmental patterns
• Economic activities and developmental activities
 Zone forming logic
• Zone is an area or stretch of land having a particular
characteristic, purpose, or use, or subject to particular
restrictions.
• For O-D survey zones are divided on the basis of
homogeneity of any factor or variable of study like
– Economic fabric
– Social fabric
– Education fabric of the society
 How zones are demarcated
• A Zone is demarcated by an imaginary line
called as the cordon line
 Methods of OD survey
• Road side interview method
• Post card method
• License method
• License plate method
• Head light on method (Car make, colour method)
• Tag on the car method
• Telephone interview method
• Home interview method
• Social media method
 Data to be collected from the survey
• Type of vehicle
• Number of occupants
• Origin and destination
• Purpose of trip
• Intermediate stop
• Travelled route
• Any other data as per the requirement
Presentation of the OD data
 Desire line
• Desire line is the imaginary line connecting
two zone center
 Locate a bridge facility

Zone X y Travellers
1 100 200 500
2 -150 -250 450
3 -250 300 250
4 250 -350 25
 No of people
willing to
Zone X y travel XN YN

1 100 200 500 50000 100000

2 -150 -250 450 -67500 -112500

3 -250 300 250 -62500 75000

4 250 -350 25 6250 -8750

1225 -73750 53750

-60.2041 43.87755
13 Jan 25 lecture 5
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 Design Steps
1. Deciding facility type (Air/road/other)
2. Demand analysis (quantum.. forecast) Expect a
3. Traffic performance analysis question
10 mark or 8
4. Size of facility (suitable to forecast) mark
5. Determine the location of a facility
6. Orientation and configuration ..
1. Like the airport runway orientation
7. Identification of Physical design standards (IRC or)
8. Geometry of facility (vehicle, human, etc)
9. Design auxiliary systems ..
1. Like the drainage., passenger lounge, hotels, etc
10. Estimate construction cost project impact
11. Future needs and expansion of facility
Prepare a detailed report including all the
above points
Transportation facility a complete design and operation
Objective Led Structure For Strategy
Elements of traffic engineering

Traffic studies and characteristics

Performance evaluation
Facility design
Traffic control
Traffic operations
Transportation systems management
Integration of intelligent transportation system
technologies
Selecting a Transportation Mode
An individual is planning to take a trip between the downtown area of two cities, A and B,. There are
three options available:
Travel by air. This trip will involve driving to the airport near city A, parking, waiting at the terminal,
flying to airport B, walking to a taxi stand, and taking a taxi to the final destination.
Travel by Taxi/Car. This trip will involve driving through several congested areas, parking in the City
area, and walking to the final destination.
Travel by rail. This trip will involve taking a cab to the railroad station in city A, a direct rail connection
to the downtown area in city B, and a short walk to the final destination.
Since this is a business trip, the person making the trip is willing to pay up to Rs 25 for each hour of
travel time reduced by a competing mode. (For example, if one mode is two hours faster than another,
the traveller is willing to pay Rs 50 more to use the faster mode.) After examining all direct costs
involved in making the trip by air, car, or rail (including parking, fuel, fares, tips, and taxi charges) the
traveler concludes that the trip by air will cost Rs 250 with a total travel time of five hours, the trip by
auto will cost Rs 200 with a total travel time of eight hours and the journey by rail will cost Rs150 with
a total travel time of 12 hours.
Which mode is selected based on travel time and cost factors alone? What
other factors might be considered by the traveler in making a final
selection?
Since travel time is valued at Rs25/hr, the following costs would be incurred:
Air: 250 + 25(5) = 375
Auto: 200 + 25(8) = 400 Actual cost of travel
Rail: 150 + 25(12) =450

In this instance, the air alternate reflects the lowest cost and is the selected mode.
However, the traveler may have other reasons to select another alternative.
These may include the following considerations
Safety.
Reliability.
Convenience
 Expect a
Question

Standard Transport Demand / Supply Function

A toll bridge carries 5000 vehicles/day. The current toll is Rs 150. When the toll is increased by Rs 25 traffic volume
decreases by 500 vehicles/day. Determine the amount of toll that should be charged such that revenue is maximized.
How much additional revenue will be received?

Let x the toll increase. Assuming a linear relation between traffic volume and cost, the expression for V is

V = 5000 - x/25 (500)

The toll is T =150 + x
Revenue is the product of toll and volume: R = (V) x (T)
Road User and Vehicle Characteristics
• Road users-drivers, pedestrians, bicyclists, and passengers
• Vehicles-private and commercial
• Streets and highways
• Traffic control devices
• The General environment
Dealing with Diversity
• Drivers and other road users, however, have widely varying
characteristics. The traffic engineer must deal with elderly drivers
as well as 18-year-olds
• Aggressive drivers and timid drivers, and drivers subject to lot of
distractions both inside and outside their vehicles.
• Reaction time,
• Vision characteristics,
• Walking speed
• Become complex because no two road users are the same
Dealing with Diversity
• Most human characteristics follow the normal distribution. The
normal distribution is characterized by a strong central tendency
(i.e., most people have characteristics falling into a definable
range).
• For example, most pedestrians crossing a street walk at speeds
between 3.0 and 5.0 ft/s. However, there are a few pedestrians
that walk either much slower or much faster
• Addressing Diversity through Uniformity is the hurdle that Traffic
Engineer has to overcome
The Driving Task
• Lunenfeld and Alexander (1990) consider the driving task to be
a hierarchical process, with three levels:
• (1) Control,
• (2) Guidance, and
• (3) Navigation.
 Road Users
• Human beings are complex and have a wide range of Characteristics that
influence the driving task
• In a system where the driver is in complete control of vehicle operations, traffic
engineering requires a keen understanding of driver characteristics
• Driver characteristics of utmost importance are
• visual acuity factors
• reaction process
• Hearing
• Physical strength
• Personality
• Psychology
• The geometric design of a highway deals with the dimensions and layout of
visible features of the highway such as alignment, sight distance and
intersection
• Geometric design of highways deals with following elements:

• Cross section elements

• Sight distance considerations
• Horizontal alignment details
• Vertical alignment details

• Intersection elements
 DESIGN CONTROLS AND CRITERIA

• The geometric design of highways depends on several design factors. The

important factors which control the geometric elements are:
• Design speed
• Topography or terrain
• Traffic factors
• Design hourly volume and capacity
• Environmental and other factors
 DESIGN CONTROLS AND CRITERIA

• Design speed : The design speed is the most important factor controlling the

geometric design elements of highways.

• In India, different speed standards have been assigned depending upon the

importance or the class of the road

• Further the design speed standards are modified depending upon the terrain

or topography.
 DESIGN CONTROLS AND CRITERIA

• Topography : The topography or the terrain conditions influence the

geometric design of highway significantly.

• The terrains are classified based on the general slope of the area across the
alignment

• Terrain Classification
Terrain classification Cross slope (%)
Plain 0-10
Rolling 10-25
Mountainous 25-60
Steep >60
 DESIGN CONTROLS AND CRITERIA

• Topography :
• The standard design speed specified for different classes of roads are different
depending on the terrain classification

• IRC recommended design speeds (kmph) in different terrains

Type Plain Rolling Hilly Steep

NH&SH 100-80 80-65 50-40 40-30
MDR 80-65 65-50 40-30 30-20
ODR 65-50 50-40 30-25 25-20
VR 50-40 40-35 25-20 25-20
 DESIGN CONTROLS AND CRITERIA

• Traffic factors :

• The factors associated with traffic that affect geometric design of roads are the

vehicular characteristics and human characteristics of road users

• The different vehicle classes : passenger cars, buses, trucks, motor cycles, and

various other types of non-motorised vehicles have different speed and

acceleration characteristics, apart from having different dimensions and

weights
 DESIGN CONTROLS AND CRITERIA

• Traffic factors :

• Human factor includes the physical, mental and psychological characteristics of

driver and pedestrian are influencing their geometrical characteristics

• PIEV Theory
I-E
• P-perception
• I-intellection
P V
• E-Emotion
• V-Volition
 DESIGN CONTROLS AND CRITERIA

• Design hourly volume and capacity :

• The traffic flow or volume keeps fluctuating with time, from a low value during

certain off-peak hours to the higher flow during the peak hours.

• It will be uneconomical to design the roadway facilities for the peak traffic flow or

the highest hourly traffic volume.

 DESIGN CONTROLS AND CRITERIA

• Design hourly volume and capacity :

• Therefore a reasonable value of traffic volume is decided for the design and this is

called the 'design hourly volume'.

• This value is to be determined from extensive traffic volume studies

 DESIGN CONTROLS AND CRITERIA

• Environmental and other factors :

• The environmental factors such as aesthetics, landscaping, air pollution, noise

pollution and other local conditions should be given due consideration in the

design of road geometrics.

 HIGHWAY CROSS SECTION ELEMENTS

• Pavement Surface Characteristics :

• The pavement surface characteristics depends on the pavement type.

• The pavement surface type is decided based on the availability of materials and

funds, volume and composition of traffic, subgrade, and climatic conditions,

construction facilities and cost considerations.

• The important surface characteristics of the pavement are:

• Friction

• Unevenness

• Light reflecting characteristics

• Drainage of surface water

 HIGHWAY CROSS SECTION ELEMENTS

• Friction :

• The friction or 'skid resistance' between vehicle tyre and pavement surface is one

of the factors determining the operating speed and the minimum distance

required for stopping the vehicles.

• When a vehicle negotiates a horizontal curve, the lateral friction developed to

counteract the centrifugal force and thus governs the safe operating speed.

• The skid resistance offered by the pavement surface is varies with driving and

surface conditions
 HIGHWAY CROSS SECTION ELEMENTS

• Friction :

• Skid' occurs when the path travelled by wheel along the road surface is more

than the circumferential movement of the wheel

• Slip occurs when a wheel revolves more than the corresponding longitudinal

movement along the roads

• While a vehicle negotiates a horizontal curve, if the centrifugal force is greater

than the counteracting forces (i.e. lateral friction and component of gravity due to

super elevation) lateral skidding takes place

 HIGHWAY CROSS SECTION ELEMENTS

• Factors affecting the friction or skid resistance :

• Types of pavement surface

• Roughness of pavement

• Condition of the pavement: wet or dry

• Type and condition of tyre

• Speed of the vehicle

• Brake efficiency

• Load and tyre pressure

 HIGHWAY CROSS SECTION ELEMENTS

• Pavement unevenness : Presence of undulations on the on the pavement surface is

called unevenness

• The longitudinal profile of the road pavement has to be even in order to provide

good riding comfort to fast moving vehicles and to minimise the vehicle operation

cost

• Pavement unevenness affects :

• Vehicle operation cost

• Comfort and safety

• Fuel consumption

• Wear and tear of tyres and other moving parts

 HIGHWAY CROSS SECTION ELEMENTS

• Pavement unevenness :

• It is commonly measure by an equipment call “Bump Integrator”

• Bump integrator measures the cumulative vertical undulations of the pavement

surface recorded per unit horizontal length.

 HIGHWAY CROSS SECTION ELEMENTS

• Light reflecting characteristics :

• Night visibility very much depends upon the light reflecting characteristics of the

pavement surface

• The glare caused by the reflection of head light is high on wet pavement surface

than on dry pavement particularly in case of black top pavement or flexible

pavement.

• Light colour or white pavement or rigid pavement surface give good visibility at night

particularly during the rain

• However white or light colour of pavement surface produces glare and eye strain

during bright sunlight

 HIGHWAY CROSS SECTION ELEMENTS

• Carriageway
• Side slope
• Shoulder
• Kerb
• Roadway width
• Guard rail
• Right of way
• Side drain
• Building line
• Other facilities
• Control line
• Median
• Camber/ cross slope
 HIGHWAY CROSS SECTION ELEMENTS

• Carriageway :

• It is the travel way which is used for movement of vehicle, it takes the vehicular loading.

• It may be cement concrete road or bituminous pavement.

• Width of carriageway is determined on (i) width of traffic lane and (ii) no of lanes

• The portion of carriageway width that is intended for one line of traffic movements is
called a traffic lane

• The width of lane depends upon the width of the vehicle and the minimum side
clearance for safety.

• Generally the width of carriage way is 3.75 m in case of single lane and 3.5 m per lane if
the pavement has two or more lanes
 HIGHWAY CROSS SECTION ELEMENTS

• Carriageway :

Single Lane Pavement

Two Lane Pavement

 HIGHWAY CROSS SECTION ELEMENTS

• Carriageway :

Class of Road Width of Carriageway (m)

Single lane 3.75
Two lanes, without raised kerbs 7.0

Two lanes, with raised kerbs 7.5

Intermediate carriageway 5.5

Multi-lane pavements 3.5 per lane

 Two lane two-way road

carriageway
 HIGHWAY CROSS SECTION ELEMENTS

• Shoulder :

• It is provided along the road edge to serve as an emergency lane for vehicle.

• Shoulder provide structural stability and support to the edges of the pavement layer

• It act as a service lane for broken down vehicles.

• The width of shoulder should be sufficient width to accommodate stationary vehicle

• It should have sufficient load bearing capacity even in wet weather condition.

• The surface of the should be rougher than the traffic lanes so that vehicles are
discouraged to use the shoulder as a regular usage.

• The capacity of the carriageway and the operating speeds of vehicles increase if the
shoulders are laid and maintained in good condition
 shoulder

Cycle track

Footpath
 Treated
unTreated shoulder
shoulder
 HIGHWAY CROSS SECTION ELEMENTS

• Width of the roadway or formation width :

• It is the sum of the width of pavement or carriageway including separators if any and
the shoulders.

• Formation or roadway width is the top width of the highway in case of embankment
section or bottom width of highway in case of cutting section

In Embankment
 HIGHWAY CROSS SECTION ELEMENTS

• Right of way :

• It is the total area of land acquired for the road along its alignment.

• It depends on the importance of the road and possible future development.

• It is desirable to acquire more width of land as the cost of adjoining land invariably
increases very much , soon after the new highway is constructed.

In Cutting
 HIGHWAY CROSS SECTION ELEMENTS

• Building line :

• In order to reserve sufficient space for future development of roads, It is

desirable to control the building activities on either side of the road boundary,

beyond the land width acquired for the road construction

• Control lines :

• In addition to “building line”, it is desirable to control the nature of building

activities upto further set back distance called “Control lines”

 HIGHWAY CROSS SECTION ELEMENTS

• Traffic separators or median :

• The main function is to prevent head on collision between the vehicle moving in

opposite direction.

• Channelize traffic into streams at intersection.

• Segregate turning traffic and to protect pedestrians.

• Rural Highway : IRC recommends a minimum desirable width of 5 m and may be

reduce to 3 m where land is restricted.

• Urban Highway : The minimum width of median in urban area is 1.2m.

4-lane divided carriage way or dual carriage way

Median/
separator
 HIGHWAY CROSS SECTION ELEMENTS

• Cross slope or camber :

• It is the transvers slope provided to the road surface to drain off the rain water
from the road surface.

• To prevent the entry of surface water into the subgrade soil through pavement.

• To remove the rain water from the pavement surface as quick as possible and to
allow the pavement to get dry soon after the rain.

• It is expressed as a percentage or 1V:Nh.

• It depends on the pavement surface and amount of rainfall.
 HIGHWAY CROSS SECTION ELEMENTS

• Shape of the cross slope :

• Parabolic shape(fast moving vehicle)

• Straight line

• Combination of parabolic and straight line

Recommended values of camber for different types of road surface
Sl no. Type of road surface Range of camber in areas of rain
fall range
heavy light
1 Cement concrete and high type 1 in 50(2%) 1 in 60(1.7%)
bituminous pavement
2 Thin bituminous surface 1 in 40(2.5%) 1 in 50(2%)
3 Water bound macadam(WBM) and gravel I in 33(3%) 1 in 40(2.5%)
pavement
4 Earth 1 in 25(4%) 1 in 33(3%)
 HIGHWAY CROSS SECTION ELEMENTS

• Kerb :

• It indicates the boundary between the pavement and shoulder.

• It is of three types

• Low or mountable kerb

• Semi-barrier kerb

• Barrier type kerb

 HIGHWAY CROSS SECTION ELEMENTS

• Low or mountable kerb :

• It allow the driver to enter the shoulder area with little difficulty.

• The height of the this type of shoulder kerb is about 10 cm above the pavement edge
with slope to help the vehicle climb the kerb easily.

• Semi-barrier kerb :

• It is provided on the periphery of a roadway where the pedestrian traffic is high.

• Height of about 15 cm above the pavement edge with a batter of 1:1 on the top 7.5 cm.

• It prevents entry of the vehicle but during emergency it is possible to drive over this kerb
with some difficulty.
 HIGHWAY CROSS SECTION ELEMENTS

• Barrier type kerb :

• It is provided in built-up area adjacent to the foot paths with considerable

pedestrian traffic.

• The height of the kerb is about 20 cm above the pavement edge with a steep

batter of 1V:0.25H
kerb
 HIGHWAY CROSS SECTION ELEMENTS

• Guard rail :

• It is provided at the edge of the shoulder when the road is constructed on a fill
exceeds 3 m.

• It is also provided on horizontal curve so as to provide a better night visibility of

the curves under the head light of the vehicle.
Guard rail
 ROAD MARGINS

• Parking lane:

• These are provided on urban roads to allow kerb parking

• As far as possible only parallel parking should be allowed as it is safer for moving
vehicle.
• It should have sufficient width say 3m

• Lay bay:

• These are provided near the public conveniences with guide map to enable
driver to stop and clear off the carriageway.

• It has 3m width,30m length with 15m end tapers on both sides.

 ROAD MARGINS

• Cycle track:

• It provided in urban areas when the volume of cycle traffic on the road is very
high.

• A minimum width of 2m is provided for cycle track.

• Footpath:

• These are provided in urban areas when the vehicular as well as pedestrian
traffic are heavy.

• To protect the pedestrian and decrease accident.

• Minimum width of 1.5m is provided.

Bus
bays
Frontage
road
c/s of highway in hilly area
c/s of road in built-up area
C/S of Flexible pavement

C/S of Rigid pavement

c/s of road in cutting
Guard rails