4. traffic engineering

Unit 4 : TRAFFIC ENGINEERING
By
Prof. Hole G.R.
Civil Engineering Department

Traffic Engineering
• Traffic engineering is a branch of civil engineering that uses engineering techniques to
achieve the safe and efficient movement of people and goods on roadways.
• It deals with the application of scientific principles, tools, techniques and findings for
safe, rapid ,economical and efficient movement of people and goods.
• The basic object of traffic engineering is to achieve efficient, free and rapid flow of
traffic with least no of accidents.

Traffic Engineering Study
 Traffic Characteristics
 Traffic Studies and Analysis
 Traffic operation-control and regulation
 Planning and analysis
 Geometric Design
 Administration and Management
1. Road user and Driver characteristics.
2. Vehicular characteristics.
Traffic Characteristics

Road user and Driver characteristics.
 Physical characteristics:
Vision, hearing, strength and reaction to traffic situation
 Mental characteristics:
Knowledge, skill, intelligence, experience, literacy
 Psychological characteristics:
Emotional factors such as fear, anger, anxiety
 Environmental factors:
Traffic stream conditions, roadside features , atmospheric conditions,
facilities to the traffic locality etc.

Vehicular characteristics.
 Static characteristics
• Dimensions
• Weight
• Maximum turning angle.
 Dynamic characteristics
• Speed
• Acceleration
• Braking characteristics
1. Effect of Width
 Width of traffic lanes
 Shoulders
 Parking facilities
2. Effect of Height
 Clearance under over bridges, under bridges,
electric & other service lines.
 Height of driver seat –provide clear vision of the
road to his front & sides.
 Height of headlight- affects sight distances at
valley curves.
3. Effect of Length
 Safe overtaking distance
 Capacity of road
 Extra widening
 Minimum turning radius
 Parking facilities
 Design of valley curves.
1. Dimensions

Vehicular characteristics.
• Design of pavement thickness
• Limiting gradients are governed by weight & power of vehicles.
• Depends on length of wheel base and features of steering system
• Affects design of sharp curves.
2. Effect Of Weight
3. Minimum Turning Radius

Traffic Studies.
• The process carried out for collecting traffic data is termed as traffic studies
• It is also called as traffic census or surveys
 A new development is proposed and it will generate substantial new traffic.
 Financial assessments are implemented (transportation impact fees).
 A major roadway improvement or reconstruction project is proposed.
 Existing transportation problems are evident, such as a high crash location or at location with
complex roadway geometrics.
 When a development is proposed for a sensitive area.
 At the judgment or discretion of jurisdiction staff based on unusual circumstances.
When should a traffic study be conducted..?

Concept of Passenger Car Unit(PCU)
 Definition:-
“ It is an conversion factor which is used to convert all different types of vehicle in
to one single unit Known as Passenger Car Unit”
• Different classes such as Car, Bus, Truck, Rickshaw, Bikes etc.
• Mixed traffic characteristics are difficult and complex for study.
• With Mixed traffic condition it is difficult to estimate traffic Volume.
• So Mixed traffic as one unit as PCU/Hr.
 Factors Affecting PCU:-
• Vehicle Characteristics:- Length, Power, Speed, etc.
• Clearance Between Vehicles,
• Traffic Stream Characteristics:- Vehicle Class, Mean Speed, Speed distribution on Stream etc.
• Road Characteristics:- Curves, Gradients, Intersection Points etc.
• Traffic Regulations:- Speed Limit, One Way Traffic, Traffic Control Devices etc.
• Environmental and Climatic Conditions.

Concept of Passenger Car Unit(PCU)

Important Definitions of Traffic Study:
1. Traffic Density:- ( No. of Veh/Km)
“It is the No. of Vehicles
present in unit length of Road at particular Time”
• In simple it is No. of Vehicle per Km at
particular time of Instant.
2. Traffic Capacity:-(No. of Veh./hr)
“ It is an Maximum No. of
Vehicles that can pass through particular section of
Road in per Unit Time”
1 km Time = 0
No. of Veh. = 0
Time = 1 hr
No. of Veh. = 6 Veh./hr

Types of Traffic Studies.
1. Volume Studies
2. Speed Studies
3. O-D Surveys
4. Parking Studies
5. Accident Studies
a. A new development is proposed and it will generate substantial new traffic;
b. Financial assessments are implemented (transportation impact fees);
c. A major roadway improvement or reconstruction project is proposed;
d. Existing transportation problems are evident, such as a high crash location or at
location with complex roadway geometrics;
e. When a development is proposed for a sensitive area
f. At the judgment or discretion of jurisdiction staff based on unusual circumstances
When should a traffic study be conducted..?

1. Volume Studies.
• Measure to quantify traffic flow
• No. of vehicles passing across a givenn traverse line of the road during unit time
• Expressed as no. of vehicles/hour or per day
• Classified traffic volume : Volume of each vehicle class separately
• Level of measurements of traffic volume
a. Hourly flow ( Veh/hour)
b. Annual Average Daily Traffic ( AADT) (Veh/day)
c. Average Annual Flow ( Veh/year)
 Purpose
1. To establish relative importance of any route or road facility.
2. To decide the priority for improvement and expansion of a road and to allot the funds
accordingly.
3. To plan and design the existing and new facilities of traffic operations on the road.
4. To make analysis of traffic pattern and trends on the road.
5. To do structural design of pavements and geometrically design of roads by classified traffic
volume study.

Methods Of Traffic Volume Studies
• Manual counts are recorded using one of three methods: tally sheets, mechanical counting
boards, or electronic counting boards
 Equipment's needed
Watch, Pencil, Eraser, Sharpener, Data Sheets, Clip Board Field summary sheets
 Advantages:-
• By this method traffic volume as well as vehicle classification and turning proportions can be
obtained.
• Data can be used immediately after collection.
 Disadvantages:-
• This method is not practicable for long duration
count and when flow is high.
• Error is common especially when volume is high.
• Count cannot be cross checked. Count cannot be
done in bad weather.
A. Manual Method

 Typical Sheet of Manual Method of Traffic Volume Study

• In this method, vehicles are counted automatically without any human involvement.
• Contact system based (pneumatic, mechanical, magnetic or piezoelectric method)
• Contactless system based (electrical/optical, ultrasound/infrared radar, micro wave, CCTV/video image
processing method etc.)
 Advantages:
• Besides traffic volume, several traffic parameters can be obtained from recorded film.
• Data can be cross checked and quality can be ensured.
• This method is suitable for long duration or continuous count.
• Count is not affected by bad weather condition.
• This method is applicable when volume is high.
• It is suitable for non-lane based traffic operation.
 Disadvantages:
• A suitable elevated place is required for filming operation.
• Data cannot be used immediately after collection.
• It requires strict lane discipline.
B. Automatic Method

Video Recording
Pneumatic Road Tube
Counter
Motion sensors
Ultrasound, light beam

2. Traffic Speed Studies
• Speed studies are necessary because the actual speed of vehicles over a particular may
vary depending on various factors such as geometric features, traffic conditions, time,
place, environment and driver.
 Speed studies can be studied under following heads-
• Travel time- it is the reciprocal of speed and is simple measure of how well road network is
operating.
• Spot Speed- it Is the instantaneous speed of a vehicle at a specified section or location.
• Average speed- it is the average of the spot speeds of all the passing vehicles at a given point on
the highway.
• Running speed- it is the average speed maintained by a vehicle over a particular stretch of road,
while the vehicle is in first motion.
• Overall speed and travel speed- it Is the effective speed with which a vehicle transverses a
particular route between two terminals.
 There are two types of speed studies carry out-
1. Spot speed study
2. Speed and delay study

 The speed at a particular moment of time at a point or cross section is termed as instantaneous or
spot speed.
 Uses Of Spot Speed Studies:-
1. Planning traffic regulation and control measure such as speed limit etc.
2. Design or redesign of various road geometry elements
3. To design the speed
4. In accident studies and preventive measure
5. Study of traffic capacity
6. To compare the behavior of diverse type of driver and vehicles under specified set of conditions
 Measurement Method Of Spot Speed
• By calculating time taken to cover a short distance
• By graphic recorder, electronic meter, photo electric meter, radar speed meter etc.
A. Spot speed study

A. Spot speed study

• It gives the particulars of running speed or fluctuation in speed the location and duration of delays or
stoppages and the overall travel speed between two desired location along a road.
• It gives information such as time, location, cause, duration and frequency of delays.
 Objectives
1. To identify the location of congestion and its cause for better improvement
2. To reduce delays and increase the travel time In benefit cost analysis
 Causes Of Delays
1. Turning vehicles
2. Parking and unparking
3. Pedestrian etc.
 Method Of Conduction
1. Floating car or riding check method
2. License plate or vehicle number method
3. Interview technique
4. Elevated observation
5. Photographic technique
B. Speed and delay study

4. Parking Studies
• To bring a moving vehicle to halt or temporarily standing or static position is termed as parking of
vehicle
• Parking is one of the major problems that is created by the increasing road traffic.
 Types of Parking:-
1. On-Street Parking
2. Off-Street Parking
• It means parking your vehicle on the street, anywhere on or along the kerb of streets, in contrast to
parking it in a parking garage.
• In some streets you can always park your vehicle on the street, but sometimes there are restrictions
through traffic signs usually controlled by government agencies itself.
 Types Of On-street Parking
1. Parallel parking
2. 30 parking
3. 45 parking
4. 60 parking
5. Right angle parking
With increase of angle of parking the capacity of vehicles increases but it requires more kerb width.
1. On-Street Parking

4. Parking Studies
• It means parking your vehicle anywhere but not on the streets.
• These are usually parking facilities like garages and lots.
• Off-street parking also includes private lots, garages and driveways
2. Off Street Parking

5. Accident Studies
 Objectives
1. To Study the causes of accidents and to suggest corrective treatments at potential locations
2. To evaluate existing design, regulations and control measures
3. To carryout before and after studies after implementing changes
4. To make computations of financial loss due to accidents
5. To provide economic justifications for the improvement measures suggested by engineers
 Causes of Accident:-
1.Drivers
Excess speed, Rash driving, Violation of rules, Failure to understand the situation,fatigue,alcohol
2.Pedestrians
Violating regulations, carelessness
3.Passengers
While alighting from or getting into vehicles
4.Vehicle defects
Failure of brakes, Steering, Lighting Systems, Tyre defects
5.Road conditions
Slippery/Skidding surface, pot holes, Ruts, Obstructions to sight

5. Accident Studies
6. Road design
Defective geometric design, Inadequate sight distance & width
7. Traffic Conditions
Vehicles moving ahead, Presence of disable vehicles
8. Weather
Like mist, Fog, Snow, Dust, Heavy Rain
9. Animals
Stray animals on the road

Traffic Regulation And Control
• It is the law rules designed to control of the movement of vehicles and pedestrians, chiefly on
city streets to prevent collisions.
• Objective of traffic regulation is safety of drivers, passengers, pedestrians, vehicles and goods.
 Consequence Of Disobeying Traffic Rules
1. Loss of life
2. Injury to people involved
3. Loss of some parts of body
4. Traffic hold up
5. Damage to the vehicle.
 Methods of Traffic Regulation
• Driver control
• Vehicle control
• Traffic flow regulation
• General controls

Traffic Control Devices
• Traffic control devices are markers, signs and signal devices used to inform, guide and control
traffic, including pedestrians, motor vehicle drivers and bicyclists
• These devices are usually placed adjacent, over or along the highways, roads, traffic facilities
and other public areas that require traffic control
• It includes...
1. Traffic signs
2. Signals
3. Markings
4. Island

1. Traffic Signs
• Traffic signs are signs which use words and/or symbols to convey information to road users.
• These devices are made with retro reflective materials that reflect light from headlights back
towards the driver's eyes. This is to achieve maximum visibility especially at night.
 Types of Traffic Signs:-
1. Regulatory Signs.
2. Warning Signs.
3. Informatory Signs.
• Traffic signs are signs which use words and/or
symbols to convey information to road users.
• These devices are made with retro reflective
materials that reflect light from headlights back
towards the driver's eyes. This is to achieve
maximum visibility especially at night.
 Types of regulatorysign
1)Stop and give way sign
2) Prohibitory sign
3) No parking and no stopping sign
4) Speed limit and vehicle control sign
5) Compulsory direction control sign
6) Restriction ends
1)Stop and give way sign
1. Regulatory Signs.

1. Regulatory Signs
2) Prohibitory sign
. 3) No parking and no stopping sign

1. Regulatory Signs
4. Speed Limit and Vehicle Control Sign
.
6. Restriction End Sign:-
5. Compulsory Direction Sign

2. Warning Signs
• The road signs are used to warn Road users of
the hazardous conditions either on or adjacent
to the road way are called warning sign.
• The warnings sign are in the shape of
equilateral triangle with its epics.
• They have a white background, red border and
black symbol
 Location of warning sign
• Urban areas- warning science should be located
at about 50 in advance from the situation
warned against
Sr.No Road Plain Area Hilly Area
1 NH & SH 120m 60m
2 MDR 90m 50m
3 ODR 60m 40m
4 VR 40m 30m

3. Informatory Signs
• The road signs used to guide Road user along
route, inform them about destination and
distance, and provide other information so as to
make the road travel is here, safe and pleasant
are called information sign and guiding sign.
• This science also include all such science which
guide users to identify points of geographical
and historical interest
 Informatory sign are of following type
1. Direction and place identification sign
2. facility information sign
3. parking sign
4. route marker sign
5. kilometer stone
6. other useful sign

Road Marking
• The lines, patterns, words, symbols or reflectors
applied to the carriage way, kerb, sides of
island or two fixed objects near the roadway
are known as traffic Road marking
• Traffic marking promote road safety and ensure
smooth flow of traffic sometimes Road
marking are used to supplement the message of
road signs and other devices
 Classification of traffic marking
a. Carriageway marking/ pavement marking
b. Kerb marking
c. Object marking
d. Reflector marking
a. Carriageway marking/ pavement marking
The traffic marking applied to the surface of road
pavement are known as carriageway marking
Types of carriageway marking
1 .centerline
These lines are provided on the roads to
separate the streams of traffic moving in opposite
directions and to facilitate their moments
10 to15 cm wide, length and 4.5 meter gap

Road Marking
2. Non passing zone marking-
Provided to indicate to the road users that over
taking is not permitted in that much portion of road
3. pedestrian crossing or crosswalk lines-
provided at places where pedestrian are to cross
the road
4.stop lines-
provided near the pedestrian crossing and at signalized
intersection to indicate the drivers to stop and then
proceed when the signal is clear distance between
pedestrian crossing and stop line at signalized
intersection varies from 2 to 3 meter

Road Marking
b. Kerb Marking
• The marking provided to kerbs of object lying
within the carriageway are known as kerb
marking.
• Provided to all islands, dividing strips of
carriageway and two kerbs directly ahead of
traffic at T junctions.
• They are used to indicate certain regulations or
increase the visibility of object s within the
carriageway from long distance.
c. Object marking
• The traffic marking provided to Physical
obstructions on or near roadway are known as
object marking.
• Provided to support the grade separation post of
signs and signals, narrow bridges, guard rails,
drums and trees etc for their clear visibility for a
long distance.

Road Marking
d. Reflector Marking
• Replacing buttons or clusters for small panels
covered with reflecting coatings provided at
kerbs are known as Reflector marking or
markers.
• Provided at kerbs to increase their visibility
specially during night hours.
e. Traffic Delineated
• Road delineators are devices or treatment of
outline the roadway or a portion there of to
provide
• visual assistance to drivers about the alignment of
road ahead, especially at night hours.
• Three types of delineators that may be used or
roadway indicators, hazard makers and object
makers.

Traffic Signals
• A set of automatically operated coloured lights, typically red, amber, and green, for controlling traffic at
road junctions, pedestrian crossings, and roundabouts.
• Used to alternately assign right-of-way to traffic moving in conflicting directions at an intersection
 Advantages
1. Provide for orderly movement of traffic
2. Increase traffic-handling capacity of an intersection
3. Reduce frequency and severity of certain types of crashes, especially rightangle collisions
4. Provide for continuous movement of traffic at a definite speed along a given route
5. Interrupt heavy traffic at intervals to permit other vehicles or pedestrians to cross
 Types
1. Traffic control
2. Pedestrian
3. Special traffic

Traffic Island
• A small raised area in the middle of a road which provides a safe place for pedestrians to stand and
marks a division between two opposing streams of traffic.
• A traffic island may be solid or painted object in a road that channelizes traffic.
• It can also be a narrow strip of island between roads that intersect at an acute angle
 Types of Traffic Island:-
1. Channelizing islands
• These are designed to control and direct traffic movement, usually turning.
2. Divisional islands
• These are designed to divide opposing or same direction traffic streams, usually through movements
3. Refuge or pedestrian islands
• Pedestrian islands are provided to serve as safety zones for the aid and protection of persons on foot.
• If a divisional island is located in an urban area where pedestrians are present, portions of each island
can be considered a refuge island
4. Rotary island
• A traffic circle is a type of intersection that directs both turning and through traffic onto a one-way
circular roadway, usually built for the purposes of traffic calming or aesthetics

Traffic Island
• A small raised area in the middle of a road which provides a safe place for pedestrians to stand and
marks a division between two opposing streams of traffic.
• A traffic island may be solid or painted object in a road that channelizes traffic.
• It can also be a narrow strip of island between roads that intersect at an acute angle
 Types of Traffic Island:-
1. Channelizing islands
• These are designed to control and direct traffic movement, usually turning.
2. Divisional islands
• These are designed to divide opposing or same
direction traffic streams, usually through movements

Traffic Island
3. Refuge or pedestrian islands
• Pedestrian islands are provided to serve as safety zones for the aid and protection of persons on foot.
• If a divisional island is located in an urban area where pedestrians are present, portions of each island
can be considered a refuge island
4. Rotary island
• A traffic circle is a type of intersection that
directs both turning and through traffic onto
a one-way circular roadway, usually built
the purposes of traffic calming or aesthetics

Road Intersection
• The places where two or more roads are arranged to join or cross at same or different level
are known as a road intersection .
• At a road intersection there are true turning and crossing traffic and their movements are
handled in different ways depending on the type of intersection and its design.
• The efficiency, safety, speed, cost of operation and capacity off road system is very much
dependent on the intersection design.
Types of road intersection:-
1.Intersection at grade
2.Grade separated intersection

Road Intersection
1.Intersection at grade:-
• The road intersection where all the Roadways join or cross at the same level are called
intersection at grade.
• Such Road intersections can be easily and economically constructed as compared to grade
separated intersection but intersections at grade provide comparatively less facility to the
crossing traffic and cause delay and resulting more number of accidents and less controlled
by traffic signals or police

Road Intersection
 Types off road intersection at grade:-
1.Cross intersection
2.T Intersection
3.staggered intersection
4.skewed intersection
5.cross skewed
6. skewed staggered
7.wye intersection
8.multiple intersection

Road Intersection
2. Intersection at Separate Grade:- (Grade Separation)
• The road intersection at which the separation in grade of the intersecting roads
is achieved by providing a bridge is called grade separated intersection
• This type of intersection causes least delay and obstruction to the crossing
traffic.
• The great separation may be achieved either by an over bridge or an
underpass.
• Transfer of root at grade separated intersection is provided by interchange
facilities of ramps.

Road Intersection
 Types of grade separated intersection
• The choice of type of grade separated intersection depends on topography, vertical alignment,
drainage, economy aesthetic features for the major highways.
• The various grade separated intersections are classified into the following two types
1. Over Pass
2. Under Pass
1. Over pass
The grade separated intersection in
which the major Highway is taken in
embankment across the other Highway
by constructing and over bridge called
overpass or flyover
• Types of Over Pass
1. Clover Leaf Flyover
2. Trumpt Type Flyover
3. Diamond Overpass

Road Intersection
 Types of Overpass
1. Clover Leaf Flyover

Road Intersection
2.Trumpt Type Flyover

Road Intersection
3. Diamond Overpass

Road Intersection
2. Underpass
• The grade separated intersection in which one highway is taken by depressing it below ground
level across the highway by constructing and under bridge is called under pass
• The underpass is advantages when the main Highway is taken along the existing grid without
alteration of its vertical alignment and the crossroad is depressed and taken underneath by
constructing and under Bridge.

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