BASED ON BTECH CIVIL ENGINEERING SYLLABUS,PRESENTATION OF TRAFFIC VOLUME STUDIES,OBJECTS OF TRAFFIC VOLUME STUDIES TRAFFIC VOLUME STUDIES IS ONE OF THE TRAFFIC ENGG. STUDIES

2. TRAFFIC VOLUME OR FLOW
Traffic volume is expressed as the
number of vehicles that cross a given
transverse line of road during unit time.
• Fast moving vehicles
(passenger cars, buses, trucks,
two wheelers)
• Slow moving vehicles (bullock
carts, cycle rickshaws)
The vehicles
are
classified
into

3. Determination of volume of each vehicle
class separately to find total volume is called
classified traffic volume studies.
Each vehicle class is converted to passenger
car unit(PCU).
Traffic flow is dynamic .
It is studied by recording direction wise
counts of each vehicle class at selected
intervals.
Or by statistical sampling techniques or short
counts.

4. Decide
priority of
road for
improveme
nt
design of road
way facilities,
compute road
capacity
Analysis of traffic
patterns &
projecting it along
identified roads
control,
plan
traffic
operatio
n.
design of
pavements
& other
structures.
assess need
for grade
separation
Control,
upgrade
intersection
turnings,signal
timings
OBJECTS OF TRAFFIC VOLUME STUDIES

5. MANUAL
COUNTS
AUTOMATIC
TRAFFIC
COUNTERS
/CLASSIFIER
METHODS OF
CLASSIFIED
TRAFFIC
VOLUME
STUDIES

6. • Enumerators are employed at pre-determined
locations to carryout classified count of vehicles &
record them at desired time intervals.
• By this method we can obtain
 Counts of different vehicle types & no. of passengers
 Turning movt of each vehicle class at intersection
 Details of pedestrian volume
 No. of commercial vehicles with load details
• Main drawback of this mthd is that it is not possible
to carry out manual count 24hrs a day all around the
year.

7. AUTOMATIC TRAFFIC COUNTERS
/CLASSIFIER
They may be fixed
or permanent or
portable type.
Old mthds of
automatic counters is
by efffect of impulses
on pneumatic hose
placed across the
roadway.
Modern sensing
techniques detect
crossing of different
vehicles based on
axle length, axle
loads.
It can work
throughout & record
exact time & speed of
vehicles & lane
occupancy.
The drawbacks are
that it cannot give
details of turning
movts,type of
commodity, vehicle
occupancy.

9. • The no.of vehicles entering from each approach leg of
intersection at fixed time intervals is counted.
• Details of queue length,waiting time,turning movt
,vehicle occupancy,no:of pedestrians were also
calculated by manual method.
• The data on turning movts of different vehicle classes
are reqrd for design of signals&grade separation.
• Data on queue length,delay at intersections,vehicle
occupancy used for economic analysis of intersection
improvement.

11. 1. Annual Average Daily Traffic(AADT)
 Obtained by determining average daily traffic
volume of the year.
 Useful to decide relative imp of routes &
phasing road development pgm
 The growth rate of different vehicle classes
can also be determined

12. 2. ANNUAL DAILY TRAFFIC (ADT)
 Traffic volume counts carried out for few days
& average daily traffic volume obtained
 Eg.Trafficcensus of non-urban roads carried
out twice a year by taking direction wise
count for a period of 7 days

13. 3. TREND CHARTS
 Show volume trends over a period of years
 Useful to estimate rate of growth &plan
future expansion
4. VARIATION CHARTS
 Show hourly,daily,seasonal variations
 Used for regulation of peak traffic hrs

14. 5. TRAFFIC FLOW MAPS
 Drawn along routes
 Give traffic volume distribution along roads
at a glance.
6. VOLUME FLOW DIAGRAM AT INTERSECTIONS
 Drawn to a scale
 Shows crossing and turning traffic needed for
intersection design

15. • Determined from plot b/w hourly traffic volume
&no:of hrs in a yr that the traffic volume is
exceeded
• Thirtieth hourly traffic volume is that which is
reached only 30 times a yr & all other hourly
volumes will be lee than this value
• The highway designed with this volume is found
satisfactory in facility & cost
• Design hourly volume can also be decided by
drawing after traffic volume studies.

17. 1. SHORT COUNTS & ADJUSTMENTS
 Becoz of requirement of large no:of
enumerators &time&financial constraints in
traffic volume count studies short counts are
adopted
 It is done for short periods of 5,10 or 15 min
at each location every hr in strategic
locations.

18. 2. EXPANDING & ADJUSTING TRAFFIC VOLUME
COUNTS
 The short term traffic volume counts made at
several locations have to be adjusted to a
common base
 AADT is the preferred measure of traffic
volume but ADT is used when it is not
available.

19. 3. ADJUSTMENTS OF COUNTS IN URBAN AREAS
 To estimate traffic volume in urban area for planning
purposecounts are made at several locations
simultaneously.
 So control stations are established in the different areas
 Traffic volume count is made continuously for 12hrs at
control stations on every day of the week
 It is averaged and daily factor for each day is developed
 Same ratios are assumed for each count stations for the
respective days of the week
 to adjust traffic volume at each count station to average
day,average count is divided by ratio found for the control
station for that day

20. 4. ADJUSTMENT OF COUNT STATION VOLUME TO
ADT
 Daily factor(DF)=7 day average for 24 hr/24
hr count on any particular day
 Seasonal factor(SF)=average24 hr traffic volume
count for 12 months/ 24
hr traffic volume count for a specific month
 24 hr traffic volume at any station on a specific
day in any of the year is adjusted to ADT as
follows
 ADT= traffic volume count x DF x SF

21. 5. COMPUTATION OF ANNUAL DAILY TRAFFIC
(AADT)
 AADT=ADT X DF X WF X SF
 WF is the weekly factor
6. PEAK HOUR FACTOR
 It is expressed in terms of traffic volume during
peak hr as a% of AADT.
 It is used for design of urban transport
infrastructure projects