Traffic Volume Study

THEORY
Traffic engineering uses engineering methods and techniques to achieve the safe and time efficient
movement of people and goods on roadways. The safe and time efficient movement of the people
and goods is dependent on Traffic flow, which is directly connected to the traffic characteristics.
The three main parameters of a traffic flow are volume, speed and density. For planning, designing
and operation of transportation system the first and foremost requirement is volume. Volume is
simply the number of vehicles passing a section of a roadway. Expressing traffic volume as number
of vehicles passing a given section of road or traffic lane per unit time will be inappropriate when
several types of vehicles with widely varying static and dynamic characteristics are comprised in
the traffic. The problem of measuring volume of such heterogeneous traffic has been addressed by
converting the different types of vehicles into equivalent passenger cars and expressing the volume
in terms of Passenger Car Unit (PCU) per hour.
Traffic Volume Study
Traffic data are needed in research, planning, designing and regulation phases of traffic engineering
and are also used in establishing priorities and schedules of traffic improvements. The traffic
engineer must acquire general knowledge of traffic volume characteristics in order to measure and
understand the magnitude, composition, and time and route distribution of volume for each area
under his jurisdiction.
Volume/flow:
The total number of vehicles that pass over a given point or section of a lane or roadway during a
given time interval is called volume. It is the actual number of vehicle observed or predicted to
passing a point during a given interval.
Passenger Car Unit (PCU)
Passenger Car Unit (PCU) is a metric used in Transportation Engineering, to assess traffic-flow rate
on a highway. A Passenger Car Unit is a measure of the impact that a mode of transport has on
traffic variables (such as headway, speed, density) compared to a single standard passenger car. It is
used to convert mix traffic into single unit.
OBJECTIVES
 To determine the peak hour traffic volume
 To determine the peak hour
 To understand the vehicle composition during the study period
 To understand the phase diagram concept
As per NRS the vehicles that fall under different PCU values are as follows:-
S.N Vehicle Type Equivalence Factor
1 Two wheelers 0.5
2 Car, Auto Rickshaw, Light Van, 1.0
pickup
3 Light truck, tractor 1.5
4 Truck, bus, Mini Bus, Tractor with 3.0
trailer
5 Non- Motorized carts 6.0
Rate of flow:
The equivalent hourly rate at which vehicles pass over a given point or section of a lane or roadway
during a time interval less than 1hr. usually 15 min.
30th highest hourly volume
It is the hourly volume that will be exceeded only 29 times in a year and all other hourly volume
will be less than this value.
Peak Hour Volume
The peak hour volume is the volume of traffic that uses the approach, lane, or lane group in question
during the hour of the day that observes the highest traffic volumes for that intersection. For
example, rush hour might be the peak hour for certain interstate acceleration ramps. The peak hour
volume would be the volume of passenger car units that used the ramps during rush hour. Notice
the conversion to passenger car units. The peak hour volume is normally given in terms of passenger
car units, since changing turning all vehicles into passenger car units makes these volume
calculations more representative of what is actually going on.
The peak hour flow rate is also given in passenger car units/hour. Sometimes these two terms are
used interchangeably because they are identical numerically.
Peak Hour Factor
The peak hour factor (PHF) is derived from the peak hour volume. It is simply the ratio of the peak
hour volume to four times the peak fifteen-minute volume. For example, during the peak hour, there
will probably be a fifteen-minute period in which the traffic volume is more dense than during the
remainder of the hour. That is the peak fifteen minutes, and the volume of traffic that uses the
approach, lane, or lane group during those fifteen minutes is the peak fifteen-minute volume. The
peak hour factor is given below.
Peak Hour Factor:
PHF = Peak hour volume/(4*Peak fifteen minute volume)
Design Flow Rate
The design flow rate or the actual flow rate, for an approach, lane, or lane group is the peak hour
volume (flow rate) for that entity divided by the peak hour factor. A simpler way to arrive at the
design flow rate is to multiply the peak fifteen-minute volume by 4. However you derive the figure,
most calculations, such as those that measure the current use of intersection capacity, require the
actual flow rate (design flow rate).

Average Daily Traffic (ADT):

The average 24-hr volume at a given location over a defined time period less than one year. The
common application is to measure an ADT for each month of the year.
Average Annual Daily Traffic (AADT):
Annual average daily traffic, abbreviated AADT, is a measure used primarily in transportation planning,
transportation engineering and retail location selection. Traditionally, it is the total volume of vehicle traffic
of a highway or road for a year divided by 365 days.

METHODS FOR VOLUME SURVEY

There are two major methods of counting vehicle for volume survey. They area.
1. Manual Counting Method
In this method, vehicles are counted manually. There are two methods of manual counting:
i) Direct Method and
ii)Indirect Method.
i. Direct Method:
Data is counted by using hand tally and manual counters/enumerators.
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.

ii. Indirect Method:

In this method, data is collected using video camera. Video is captured for long time and data is
collected later by rewinding.
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 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. This process is time consuming and tedious. Because of limitation of
capacity of film, it is not suitable for long duration counts. Quality of video recorded on film is
dependent on intensity of light and this method is not suitable in overcast days.
2. Automatic counting method:
In this method, vehicles are counted automatically without any human involvement. There are two
techniques of automatic counting: a) Contact system based on pneumatic, mechanical, magnetic or
piezo-electric method and b) Contactless system based on electrical/optical, ultrasound/infrared
radar, micro wave, CCTV/video image processing method etc.
Advantages: This method is suitable for long duration or continuous count. It is used as permanent
counting station. It does not need manpower and is free from human error. Data is obtained in usable
format. It is less expensive as manpower is not needed. Count is not affected by bad weather
condition.
Disadvantages: It requires strict lane discipline. Non-motorized vehicles are hard to detect by this
method. Detailed classification of vehicle is not possible. Accuracy is less than manual method.
Installation cost is high.

Figure 1:- Data Collection Sheet

Procedure

Observation, Calculation and data presentation

 Direction: From…………………….
To Left Through To Right
light Truck, Heavy light Truck, Heavy light Heavy
Time Car, Mini Car, Mini Car, Mini
Bike, by- tractors trucks, Bike, by- tractors trucks, Bike, by- Truck, trucks, Total(PCU)
van,Jeep, van,Jeep, van,Jeep,
cycle etc. Tractors, cycle etc. Tractors, cycle tractors Tractors,
taxi etc. taxi etc. taxi etc.
Bus Bus etc. Bus
8:30 - 8:45

8:45 - 9:00

9:00 - 9:15

9:15 - 9:30

9:30 - 9:45

9:45 - 10:00

10:00 -
10:15
10:15 -
10:30
TOTAL

RESULT

DISCUSSION AND CONCLUSION