introduction of traffic engineering

1. Traffic Engineering
Mr.P Umasai Krishna M.tech,(Ph.d)

2. Scope of traffic Engineering:
 Traffic Characteristics
Traffic studies and analysis
Planning and analysis
Geometric design
Traffic operation, regulation and control
Road safety
Administration and management

5. Traffic volume studies
Spot speed studies
Speed and delay studies
O & D studies
Parking studies
Accident studies

6. Units-No of vehicles/ time
In order to express the total traffic flow on road per unit time,
it is necessary to convert the flow of different vehicle
classes into one standard vehicle type, such as the ‘Passenger
Car’.
Therefore each vehicle class is assigned an equivalency factor
called ‘passenger car unit(PCU)’
Peak hourly volume is generally much higher than the
average hourly volume of the entire day.

7. To decide the priority for improvement & up gradataion of
roads
For re-design of road facilities.
For analysis of traffic patterns
For computing roadway capacity
To plan traffic operation & control of existing facilties
To plan and design new facilities
Turning movement studies at intersection are used to design
signals
For structural strengthening of pavement and other road way
system

12. Planning traffic regulation and control measures
Design or redesign if various geometric elements
To decide design speed of existing or new facilities
In accident studies and preventive measures
Study of traffic capacity
To final the speed trends with respect to last several years

13. Pavement width
Horizontal curve
Sight distance
Gradient
Pavement unevenness
intersections
Road side developments

14. Speed distribution tables: From the spot speed data of the
selected samples, frequency distribution table of spot speed is
prepared by arranging the speed groups covering desired speed
ranges and the number of vehicles in each speed range
The A.M of the measured speeds is taken as average spot
speed of all the vehicles in the stream.

16. Methods of conducting speed and delay studies:
a) Floating car method
b) License plate
c) Interview technique
d) Elevated method
e) Photographic method

21. Mean values of speed and delay
Directio
n
N-S
Journey
time
Min-sec
Stopped
delay
Min-sec
Overtaki
ng
Overtak
en
In
opposite
direction
Total 26-00 6-00 14 20 1088
Mean 6-30 1-30 3.5 5 272
S-N
Total 30-24 7-12 12 8 716
Mean 7-36 1-40 3 2 179

22. North-south direction
 Ny = avg no of vehicles overtaking minus overtaken = 3.5-5= -1.5
 Na= avg no of vehicles during trips in opposite direction = 179
 Tw = avg journey time with the stream q =6.5min
 Ta= Avg journey time during trip against the stream =7.6
 Avg volume = 179-1.5
7.6+ 6.5
= 12.59 veh/min
Avg journey time = 6.62min
Avg journey speed = 3.5*60/6.62 =31.7kmph
Avg stopped delay = 1.5min
Avg running time = Avg journey time- avg stopped delay
=5.12min
Avg running speed= 3.5*60/5.12 = 41kmph
Similarly we can calculate for S-N direction

23. License plate method
 Synchronized stop watches or voice recording equipment are
used
 Observers are stationed at the entrance and exit of the test
stretch where information of travel time is required.
 The timings and vehicle numbers are noted.
 From the office travel time of the each vehicle could be found
 But the method does not give important details such as causes
of delays and duration and number of delays within the test
stretch.

24. Interview method
 The work can be completed in a short time by interviewing and
collecting the required details from the road users on the spot
 Data on delays collected depend on the assessment of each
individual driver
 This method may not provide with all the required details
correctly
 Photographic technique:
 Observers with timers are located at an elevated observation
point from where the movement of most of the vehicles within
the desired stretch
 Alternatively cameras or video equipment are located and the
desired observations recorded.
 It is suitable for short stretches

25. O & D studies:
It provides the basic data for determining the desired direction
of vehicular flow or passenger trips in terms of the desired lines.
Desired lines are straight lines joining the points of o&d of each
trip

26. Methods of conducting O & D studies
 Road side interview method
 License plate method
 Return post card method
 Tag-on-car method
 Home interview method

27. Road side interview
 The vehicles are stopped at selected interview stations by a group of
persons.
 The data is collected on spots in the prescribed formats.
 The information includes place, time of origin & destination, route,
location of intermediate stoppages.
 Part of the traffic may be filtered and diverted through a prescribed
lane with the help of police and warning signs.
 The answers to the set of questionnaire are noted by the enumerators
and the vehicles are allowed to proceed with minimum possible
delay.
 Data can be collected in short duration and team can be trained
quickly.
 The main drawback is some delay to road users and also congestion
due to the stopped vehicles.

28. License plate method
 The entire area under study is surrounded by police and the
enumerators are stationed on all observation stations on all the
roads leading in and out of the area.
 Enumerators note the registration number of the vehicles
entering and leaving the cordoned area and the time
 Separate recording sheets are maintained for each direction of
movement for a specified time interval.
 The major work will be office computations and analysis, by
tracking each vehicle number and its time of entering and
leaving the area.
 This method is quite easy and quick as far as the field work is
concerned.

29. Return post card method:
 Reply post cards with return address are distributed to the road
users at some selected points along the route
 The questionnaire to be filled in by the road users is printed on
the card, along with a request for co-operation and purpose of
the study.
 The distributing stations for the cards may be selected where
vehicles have to stop as in case of a toll booths or signals.
 This method is suitable where the traffic is heavy
 .
 The personnel need not be skilled or trained just for
distributing the cards.
 Only a part of the road users may return the cards promptly
after filling in the desired details properly and correctly.

30. Tag on car method
 In this method a pre coded card is stuck on the vehicle
as it enters the area under study.
 When the car leaves the cordon area the other
observations are recorded on the tag.
 This method is useful where the traffic is heavy and
moves continuously.

31. Home interview method
 This method is preferred when comprehensive traffic and
transportation requirements are to be planned for a city.
 A random sample of 0.5 to 10 percent of the population it selected
depending on the total number of residences.
 It is desirable to classify the types of the households in the entire
study area and then randomly select the samples from each class.
 The residences are visited by the trained personal and they collect the
travel data from each member of the house hold.
 Detailed information regarding the trips made by the members is
obtained on the spot.
 The data collected will be useful either for planning the road network
and other roadway facilities for the vehicular traffic or for planning
the mass transportation requirements of the passenger trips or for
both the requirements
 Socio-economic and other details may be collected so as to be useful
for forecasting traffic and transportation growth.

32. Presentation of O-D data
 O and D tables are prepared showing number of trips between different
zones.
 Desire lines are plotted which is graphical representation prepared in almost
all O and D surveys.
 They are straight lines connecting the origin points with destinations,
summarized into different area groups.
 The width of the such desire lines is drawn proportional to the number of
trips in both direction.
 The desire lines helps to find the necessity of a new road link, a diversion, a
by-pass or a new bridge.
 The lines are used to plan mass transport facilities.
 Contour lines may be plotted similar to topographic contours.