Which formula can be used to determine the average headway on a road?

The formula that determines the average headway on a road is best represented as headway equals spacing divided by speed. This relationship is grounded in the definitions of headway and the components of traffic flow.

Headway refers to the time interval between two vehicles as they pass a specific point on the road. It is a measure of how closely vehicles follow one another. The spacing refers to the distance between the front of one vehicle and the front of the next vehicle in the traffic stream. When you divide this spacing by the speed of the vehicles (which is the rate at which they are moving), you effectively convert that spatial separation into a temporal measure, providing the average time interval, or headway.

To clarify why this formula is appropriate, consider that if vehicles are traveling at a constant speed, the time taken for a vehicle to travel the distance corresponding to the spacing will give the average headway. As speed increases, the time interval reduces, indicating shorter headways, and vice versa.

This concept is essential in traffic engineering, where understanding headways can help in determining safe following distances, optimizing traffic flow, and reducing congestion.