Traffic Volume Count

What is Traffic Volume Count ?

Traffic Volume Count is recording/counting of number of vehicles passing through a road over a period of time. It is usually expressed in terms of Passenger Car Unit (PCU) and measured to calculate Level of Service of the road and related attributes like congestion, carrying capacity, V/C Ratio, identification of peak hour or extended peak hour etc.  Traffic volume count or TVC is usually done as a part of transportation surveys, TVC can be classified or unclassified.

Traffic Volume Count

Need of Traffic Volume Count Survey

Traffic Volume Survey is an essential part of Town Planning, especially for a town planner. It includes counting the number of vehicles passing through a survey station.

The study of Classified Traffic Volume Count is to understand factors that form the basis of:

a) Checking the efficiency/saturation of the road network by comparing current traffic volume with the calculated capacity or by identifying level of service
b) Establishing the use of the road network by vehicles of different categories, traffic distribution, PCU/vehicle value
c) Need of median shifting or road widening

Purpose of Traffic Volume Count

The purpose  classified traffic volume count is to draw inferences on the basis of data collected. To provide possible solutions and improvement suggestion for the problem identified. The objectives covered in it includes  identifying the hourly distribution of vehicles and peak hour, identify level of service and compare modal composition on different hierarchy of roads in our study area.

Pre Requisite Knowledge

Assessment of available resources prior to commencement of any activity is critical to any assignment at hand, hence proper evaluation of the extent or scope of the counting (quality level of data required) was undertaken. The following points were kept in mind before starting of the survey.

1)     Location of the station
2)     Quality of data to be collected
3)     Level of traffic flow
4)     Manpower available

Methods of doing Traffic Volume Count

Traffic Volume Count can be done by various methods depending upon various factors like manpower available, budget, technology/instrument available, magnitude of traffic data required or to be collected which will then determine quality and type of vehicle classification to be adopted. Traffic counting falls in two main categories, namely: manual count and automatic count.Traffic data collection forms the integral part of traffic volume study as it provides the raw data and includes primary survey. The various types and methods used to collect traffic data not only provide a good and valuable coverage of the required traffic information. Different methods of traffic volume count are as mentioned below –

Duration and Interval of Traffic Counts
In order to predict traffic flow volumes that can be expected on the road network during specific periods, knowledge of the fact is required that traffic volumes changes considerably at each point in time. There are three important cyclical variations:

Hourly pattern: the way traffic flow characteristic varies throughout the day and night;

Daily Pattern: The day-to-day variation throughout the week

Monthly and yearly Pattern: The season-to-season variation throughout the year.

  1. Manual Count

The most common method of collecting traffic volume data is the manual method of traffic volume count,  which involves a group of people recording number of vehicles passing, on a pre-determined location, using tally marks in inventories. Raw data from those inventories is then organized for compilation and analysis.

This method of data collection can be expensive in terms of manpower, but it is nonetheless necessary in most cases where vehicles are to be classified with a number of movements recorded separately, such as at intersections also in case where automatic methods cannot be used due to lack of infrastructure, necessary authorization etc.

    2. Automatic Count

This method is employed in cases where manual count method is not feasible. Various instruments are available for automatic count, which have their own merits and demerits. Some of the widely used instruments are pneumatic tubes, inductive loops, weigh-in-motion Sensor, micro-millimeter wave Radar detectors and video camera.

Both types of count can be classified or unclassified. Classified traffic volume count gives a better understanding of the types of vehicles which uses the road and can be used for number of other purposes apart from the transportation surveys. It can also be used for calculating the modal split of vehicles on the road.

Unclassified traffic volume count is done where sufficient manpower is not available or the budget for the survey is low. This type of volume count does not give a good information about the road.

Factors to be considered while doing a traffic volume survey on mid block –

1. Surveyor should not effect the flow of traffic.
2. Survey station should be located at position where queuing do not take place.
3. Vehicles should be classified if possible as it saves time for Classified Traffic Volume Survey. Also classified results have many other application.
4. Safety of surveyor should be kept in mind and safe location should be selected. This becomes more important in rural area where carriageway is not well defined.
5. Equipments used while automatic count should be placed such that they do not draw attention of driver.

Traffic Volume Survey can be done manually or by use of automatic methods depending upon various factors like manpower available, budget, technology/instrument available, magnitude of traffic data required

Read about: Trip Generation, Traffic Island & its Use