Traffic Engineering and Safety

DR. MARISAMYNATHAN S
A P/C E
NIT T RIC H Y
Module 4
Traffic Management:

➢ Parking studies – parking statistics, parking surveys, parking requirements - on

➢ Lay-byes and bus stops.

➢ Principles of Traffic Control: Basics of traffic management. Traffic Signs, Road

➢ Traffic System Management – speed, vehicle, parking, enforcement regulations.

➢ Mixed traffic regulations – one way, tidal flow, turning restrictions etc.

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Parking system
➢ On street parking
➢ On street parking means the vehicles are parked on the sides of the street itself.

➢ This will be usually controlled by government agencies itself.

➢ This classification is based on the angle in which the vehicles are parked with
respect to the road alignment.

➢ As per IRC the standard dimensions of a car is taken as 5× 2.5 meters and that for a
truck is 3.75× 7.5 meters.

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Type of on street parking
1. Parallel Parking –
◦ The vehicles are parked along the length of the road.

◦ Here there is no backward movement involved while parking or unparking the

◦ Hence, it is the most safest parking from the accident perspective.

◦ However, it consumes the maximum curb length and therefore only a minimum
number of vehicles can be parked for a given kerb length.

◦ This method of parking produces least obstruction to the on-going traffic on the
road since least road width is used.
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Type of on street parking
2. 30∘ parking–
◦ In thirty degree parking, the vehicles are parked at 30∘ with respect to the road
alignment.

◦ In this case, more vehicles can be parked compared to parallel parking.

◦ Also there is better maneuverability.

◦ Delay caused to the traffic is also minimum in this type of parking.

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Type of on street parking
2. 45∘ parking–
◦ As the angle of parking increases, more number of vehicles can be parked.

◦ Hence compared to parallel parking and thirty degree parking, more number of
vehicles can be accommodated in this type of parking.

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Type of on street parking
2. 60∘ parking–
◦ The vehicles are parked at 60∘ to the direction of road.

◦ More number of vehicles can be accommodated in this parking type.

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Type of on street parking
2. Right Angle parking–
◦ In right angle parking or 90∘ parking, the vehicles are parked perpendicular to
the direction of the road.

◦ Although it consumes maximum width kerb ,length required is very little.

◦ In this type of parking, the vehicles need complex maneuvering and this may
cause severe accidents. This arrangement causes obstruction to the road traffic
particularly if the road width is less. However, it can accommodate maximum
number of vehicles for a given kerb length.

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Type of on street parking

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Off street parking
➢ In many urban centers, some areas are exclusively allotted for parking which will be
at some distance away from the main stream of traffic. Such a parking is referred to as
off-street parking.

➢ They may be operated by either public agencies or private firms.

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Parking requirements
➢There are some minimum parking requirements for different types of building.
➢ For residential plot area less than 300 sq.m require only community parking space.

➢ For residential plot area from 500 to 1000 sq.m, minimum one-fourth of the open
area should be reserved for parking.

➢ Offices may require at least one space for every 70 sq.m as parking area.

➢ One parking space is enough for 10 seats in a restaurant where as theatres and
cinema halls need to keep only 1 parking space for 20 seats.

➢ Thus, the parking requirements are different for different land use zones.

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 Ill effects of parking
➢ Congestion

➢ Accidents

➢ Environmental Pollution

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Parking statistics
➢ Parking accumulation: It is defined as the number of vehicles parked at a given
instant of time. Normally this is expressed by accumulation curve. Accumulation curve
is the graph obtained by plotting the number of bays occupied with respect to time.

➢ Parking volume: Parking volume is the total number of vehicles parked at a given
duration of time. This does not account for repetition of vehicles. The actual volume of
vehicles entered in the area is recorded.

➢ Parking load : Parking load gives the area under the accumulation curve. It can also
be obtained by simply multiplying the number of vehicles occupying the parking area
at each time interval with the time interval. It is expressed as vehicle hours.
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Parking statistics
➢ Average parking duration: It is the ratio of total vehicle hours to the number of
vehicles parked.

➢ Parking turnover: It is the ratio of number of vehicles parked in a duration to the

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Parking statistics
➢ Parking index: Parking index is also called occupancy or efficiency. It is defined as
the ratio of number of bays occupied in a time duration to the total space available. It
gives an aggregate measure of how effectively the parking space is utilized. Parking
index can be found out as follows

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Example
➢ To illustrate the various measures, consider a small example in figure, which shows
the duration for which each of the bays are occupied (shaded portion). Now the
accumulation graph can be plotted by simply noting the number of bays occupied at
time interval of 15, 30, 45 etc. minutes is shown in the figure.

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Example
➢The various measures are calculated as shown below:
➢ Parking volume is given as 5 vehicles.

➢ Parking load is given as (1 + 2 + 1 + 0 + 1 + 2 + 3 + 1)*15/60 = 2.75 veh-hour.

➢ Average parking duration is computed as 2.75 veh-hours/5veh= 33 minutes.

➢ Parking turnover is obtained as (5-veh ∕ 2-hours) / 3bays= 0.83 veh/hr/bay.

➢ Parking index is calculated as (2.75-veh-hour/ 3×2 veh hours) × 100= 45.83%

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Parking surveys
1. In-out Survey

2. Fixed period sampling

3. License plate method of survey

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In-out Survey
From an in-out survey conducted for a
parking area consisting of 40 bays, the initial
count was found to be 25. Table gives the
result of the survey. The number of vehicles
coming in and out of the parking lot for a
time interval of 5 minutes is as shown in the
table. Find the accumulation, total parking
load, average occupancy and efficiency of the
parking lot.

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In-out Survey

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In-out Survey

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License plate method of survey
➢The parking survey data collected
from a parking lot by license plate
method is s shown in the table. Find
the average occupancy, average
turn over, parking load, parking
capacity and efficiency of the
parking lot.

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License plate method of survey

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License plate method of survey

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Lay-byes and bus stops

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Lay-byes and bus stops

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Lay-byes and bus stops

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Lay-byes and bus stops

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Lay-byes and bus stops

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Lay-byes and bus stops

IRC 80 – 1981: Type Designs for Pick-up bus stops on rural highway

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Principles of Traffic Control
➢ Conflicts at an intersection

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Principles of Traffic Control
➢ Two methods of intersection controls are there: time sharing and space sharing.

➢ The type of intersection control that has to be adopted depends on the traffic
volume, road geometry, cost involved, importance of the road etc.

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Levels of intersection control
➢The control of an intersection can be exercised at different levels.

➢ They can be either passive control, semi control, or active control.

➢ In passive control, there is no explicit control on the driver.

➢ In semi control, some amount of control on the driver is there from the traffic
agency.

➢ Active control means the movement of the traffic is fully controlled by the traffic
agency and the drivers cannot simply maneuver the intersection according to his
choice.

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Passive control
1. No control

2. Traffic signs

3. Traffic signs plus marking

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Semi control
1. Channelization

2. Traffic rotaries

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Active control
1. Traffic signals

2. Grade separated intersections

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Traffic Signs
▪ Symbols on portable support provided on roads to give information, warning and
guidance to the road users are known as traffic signs or road signs.

▪ Necessity of Road Signs

▪ To regulate the traffic

▪ To provide safety to the traffic

▪ To expedite the traffic

▪ To guide the traffic by supplying information about directions and point of interest

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Classification of Traffic Signs
➢Cautionary or warning signs

➢Regulatory signs

➢Informatory Signs

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Cautionary or Warning Signs
➢Used to warn the road users of certain hazardous situations on and adjacent to the
roadway

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Cautionary or Warning Signs

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Cautionary or Warning Signs

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Mandatory or Regulatory Signs
➢These road signs are used to inform road user about certain laws, regulations,
prohibition or restrictions which have to be complied with and any case of non-
compliance are liable to legal action.

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Mandatory or Regulatory Signs

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Mandatory or Regulatory Signs

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Mandatory or Regulatory Signs

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Informatory Signs

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Road markings
➢ Road markings are a psychological barrier and an important component of a
highway, which function in guiding and controlling the traffic.

➢ It also channelizes the pedestrians and cyclists movement into a safe location
ensuring smooth and orderly flow of traffic and for promoting road safety.

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Road markings
➢Types
1. Longitudinal Markings

2. Transverse Markings

3. Hazard Marking

4. Block Marking

5. Arrow Marking

6. Directional Marking

7. Facility Marking

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Road markings
➢Types
Longitudinal Markings

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Road markings
➢Types
Transverse Markings

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Road markings
➢Types
Hazard Marking

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Road markings
➢Types
Arrow Marking

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Traffic System Management

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Traffic System Management - Speed
➢ Traffic Calm Measures - IRC 99 : 2018 captioned “Guidelines for traffic calming measures in urban and rural areas”
stipulates various traffic calming measures including raised pedestrian crossings, rumble strips etc.
➢ Speed bumps, sometimes split or offset in the middle to avoid delaying emergency vehicles
➢ Speed humps, parabolic devices that are less aggressive than speed bumps.
➢ Speed cushions, two or three small speed humps sitting in a line across the road that slow cars down but allows wider emergency
vehicles to straddle them so as not to slow emergency response time.
➢ Speed tables, long flat-topped speed humps that slow cars more gradually than humps
➢ Raised pedestrian crossings, which act as speed tables, often situated at junctions.
➢ Speed dips, sunken instead of raised (often seen as double dips in cycleways in The Netherlands)[12]
➢ Changing the surface material or texture (for example, the selective use of brick, cobblestone, or polymer cement overlay). Changes in
texture may also include changes in color to highlight to drivers that they are in a pedestrian-centric zone.
➢ Rumble strips, when placed perpendicular to traffic in the travel lane (rather than placed between lanes parallel to traffic) act as
speed bumps as they produce unpleasant sounds and vibration when crossed at higher speeds.

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Traffic System Management - Speed

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Traffic System Management - Parking
➢ Automated parking barrier systems

➢ Public Parking

➢ Office Centric

➢ Residential

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Traffic System Management - Parking

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Traffic System Management - Vehicle

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Traffic System Management - Enforcement
➢ MoRTH

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Mixed Traffic Regulations
1. One way

2. Tidal flow - This is a 'reversible' lane in which traffic may travel in either direction
depending on the time of day or traffic conditions. It is designed to improve traffic
flow during peak periods by making an extra lane available for vehicles travelling
along the busier side of the road.

3. Turning restrictions

4. Exclusive bus lanes

5. Closing of side streets

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