Road User Characteristics, Vehicle Characteristics, PIEV Theory, Traffic Studies, Volume Studies,Speed Studies, Origin Destination Studies, Accident Studies,

1. TRAFFIC ENGINEERING
TE/BE/2016-2017 Part II

2.  Traffic Characteristics
 Road user characteristics
 Vehicular characteristics
 Traffic studies
 Name of various studies & Uses
 Accident studies
 objectives, causes, diagrams, preventive measures
 Traffic regulations & Control Devices
 Signs, signals, markings, islands, intersections
 Parking facilities

3. Road user
characteristics
Physical
Vision
Hearing
Strength
Reaction to
situations
PIEV theory
Psychological
Attentiveness
Fear/Anger
Attitude
Environmental
Road side
features
Atmospheric
conditions

4. PIEV Theory
 Perception Time : Time required to perceive an
object
 Intellection Time: Time required for the driver to
understand the situation
 Emotion Time : Time elapsed during emotional
sensations. Eg. Fear,anger,shocking etc
 Volition Time : Time taken by the driver for the
final action. Eg. Braking
Total Reaction Time >> 0.5 sec to 3 or 4 sec
Say it as 2.5 sec on an average

5. Vehicular
Characteristics
Static
Characteristics
Vehicle Dimensions
Maximum Turning
Angle
Weight of loaded
vehicles
Dynamic
Characteristics
Power of vehicles
Speed of vehicles
Braking
characteristics
Acceleration &
Decceleration

6. Vehicle Dimensions
Length & Width of vehicle
 Width of traffic lane
 Shoulders, Parking facilities
 Capacity of roads
 Design of vertical & horizontal alignment
 Extra width of pavement
 Safe overtaking distance
Height of vehicle
 Clearance to be provided under structures such
as bridges, underpasses, electric lines etc

7. Maximum Dimension Of Road Vehicles
Dimensions of
vehicles
Details Maximum dimensions
( Excluding front & rear
Bumpers), m
Width All Vehicles 2.50
Height
Single deck vehicle for normal
application
3.80
Double deck vehicle 4.75
Length
Single unit truck with two or
more axles ( type 2,3)
11.00
Single unit bus with two or
more axles (type 2,3)
12.00
Semi trailer tractor combination
( Type 2-S1,2-S2,3-S1,3-S2)
16.00
Tractor & Trailer combination (
Type 2-2,Type 3-2,2-3,3-3)
18.00

9. Weight of loaded vehicle
 Affects – design of pavement thickness & Gradient
 IRC recommends maximum permissible gross weight
& axle weights
Power of vehicle
 Governs the limiting values of gradient on roads
 Consider : total resistance to traction, rolling
resistance, air & grade resistance
 From total hauling capacity >>> speed & acceleration
of vehicles are determined

10. Speed of vehicles
 Affects design of sight distance
 Superelevation
 Length of transition curves
 Design gradients
 Capacity of traffic lane
 Design of Control measures
Braking Characteristics & Efficiency
 Deceleration and braking characteristics
 Safety of operation, sight distance, spacing
 Braking efficiency to be 100 %
Braking
system

11. TRAFFIC STUDIES
 Traffic volume
 Spot speed
 Speed & Delay
 Origin & Destination
 Parking
 Accident

12. Traffic Volume Studies
 Measure to quantify traffic flow
 No. of vehicles passing across a given
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
 Hourly flow ( Veh/hour)
 Annual Average Daily Traffic ( AADT) (Veh/day)
 Average Annual Flow ( Veh/year)

13. Methods for traffic counts
( Traffic Volume )
Manual Method
 No. of observers needed
 Equipments needed
 Watch, Pencil, Eraser, Sharpner, Data Sheets, Clip Board
 Field summary sheets
Automatic Method ( Devices)
 Sensors
 Pneumatic Tubes, Electric Contact, Coaxial Cables
 Photoelectric devices, Radar, Infrared/ Ultrasonic devices
 Magnetic devices
 Recording Mechanism
 Video/Photographic Method

14. Traffic volume count ( Manual)

15. Traffic volume count ( Automatic)

16. Traffic Speed Studies
 Change in speed of vehicles
 Change in Level Of Service (LOS) of the roads
Spot Speed Studies:
 Instantaneous speed of a vehicle at specific
location
 Method of measuring :
 time taken to cover a known distance
 Long – base Method
 Short – base Method

17.  Radar Speed meter
 Photographic Method
 Data presented as cumulative speed
distribution diagram

18. Speed & Delay Studies
 Running speed, fluctuations in speeds,
 Overall travel speed
 Location, duration & frequency of delays
 Measuring Methods:
 Floating car
 License plate / vehicle registration number
 Interview technique
 Elevated observations
 Photographic

19. O – D Studies
 Basic data for determining “ Desired Lines”
 Establish preferential routes for different trips
 Methods of conducting :
 Road – side interview
 License plate
 Return – post card
 Tag on car
 Home – interview method
 Work spot interview method
 Presentation of data
 Showing no. of trips between different zones
 Desire lines are plotted connecting Origin & Destination

21. ACCIDENT STUDIES
 Objectives
 To Study the causes of accidents and to suggest
corrective treatments at potential locations
 To evaluate existing design, regulations and
control measures
 To carryout before and after studies after
implementing changes
 To make computations of financial loss due to
accidents
 To provide economic justifications for the
improvement measures suggested by engineers

22. Causes of accidents
 Drivers
 Excess speed, Rash driving, Violation of rules,Failure to
understand the situation,fatigue,alcohol
 Pedestrians
 Violating regulations,carelessness
 Passengers
 While alighting from or getting into vehicles
 Vehicle defects
 Failure of brakes, Steering,Lighting Systems,Tyre defects
 Road conditions
 Slippery/Skidding surface, pot holes, Ruts, Obstructions
to sight

23.  Road design
 Defective geometric design, Inadequate sight
distance & width
 Traffic Conditions
 Vehicles moving ahead, Presence of disable
vehicles
 Weather
 Like mist, Fog, Snow, Dust, Heavy Rain
 Animals
 Stray animals on the road

24. Collision Diagram
 Drawn not to scale
 Depict the details of the accident location
 shows appropriate path of the vehicles and
pedestrians involved in accident
 Shows other objects with which the vehicles
have collided
 Most useful for Before and After studies

26. Condition Diagram
 Drawn to Scale
 Shows all important physical features of the
road and adjoining area
 Important details to be shown are
 Width of roadway shoulders,medians,curves,kerb
lines, Roadway conditions, Obstructions if any
 Both Collision & Condition diagrams can be
combined together

28. Accident Reduction Measures
EngineeringMeasures
• Road Designs
• Preventive
Maintenance of
Vehicles
• Before and After
Studies
• Road Lighting
EnforcementMeasures
• Speed Control
• Traffic Control
Devices
• Training and
Supervision
• Medical Check
• Observance of
law and
regulations
EducationalMeasures
• Instructions in
Schools
• Poster
exhibition
• Publishing
Highway
Safety Code
• Organizing
Traffic Safety
Awareness
Programs