Traffic Density Calculator

Created by Bogna Szyk
Last updated: Oct 31, 2018

This traffic density calculator helps you analyze the traffic on any road. Thanks to this tool, you will be able to estimate what is the traffic flow and traffic density, as well as find out the average travel speed. You will also estimate the average distance between two consecutive cars on the road.

Keep reading to learn how to calculate the traffic density and flow, or take a look at our MPG calculator!

What is the traffic flow?

Traffic flow is defined as the number of vehicles that pass by a point in a given time period. This value is usually expressed as an hourly rate - for example, you can observe a flow of 500 vehicles per hour on a highway.

Traffic flow is usually measured by observing a road and noting down the number of vehicles passing you by. To convert this number into the hourly rate, you need to use the following equation:

flow = n / t

where n is the number of vehicles that passed by a point during the time frame t.

The flow is equal to zero in two cases - either when there is no traffic (no cars present on the road), or when all vehicles are stuck in a traffic jam and cannot move forward.

Traffic density formula

Traffic density is a second fundamental characteristic of any road. It tells you how significant is the congestion of cars on the road. If the density reaches its maximum, the flow drops to zero, as a traffic jam is formed.

The density is measured as the number of vehicles m that occupy a segment of a road of a length L. To calculate it, simply divide these two values:

density = m / L

The reciprocal of the traffic density is the headway - the distance between the front tip of two vehicles driving one after another.

How to calculate average travel speed

The two values above - flow and density - are directly linked to the average travel speed. These three are called the fundamental characteristics of a traffic flow and are linked with the following formula:

flow = speed * density

This fundamental equation gives you the most basic information about the traffic on any road.

To calculate the travel speed with this traffic density calculator, follow these steps:

  1. Measure how many vehicles pass one point in a given time frame. We can assume that during two minutes, 20 cars passed you by. It means that the traffic flow is equal to

flow = 20 / 2 = 10 veh / min = 600 veh / h

  1. Count how many vehicles occupy a segment of a road at once. Let's say that on a segment of length 200 m, you spotted two cars. The traffic density is equal to

density = 2 / 200 = 0.01 veh / m = 10 veh / km

  1. Now, you can calculate the headway between the cars as the reciprocal of the density:

headway = 1 / 10 km = 100 m

  1. The last thing to do is to use the fundamental equation in order to find the average travel speed:

flow = speed * density

speed = flow / density

speed = 600 / 10 = 60 km/h

  1. The average travel speed on this road is equal to 60 km/h.

Make sure to take a look at our gas calculator, too!

Bogna Szyk
Traffic flow
No. of vehicles
that pass during...
Traffic flow
per h
Traffic density
No. of vehicles
on a road of length...
Average speed
Travel speed
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