What is the basic equation for uninterrupted flow in traffic engineering?

In traffic engineering, the basic equation for uninterrupted flow relates to the relationship between volume, speed, and density. The correct representation of this relationship is given by the formula: speed (v) equals density (D) divided by space mean speed (S).

This equation is fundamentally derived from the flow theory in traffic, where the following relationships are noted: Flow (q) is equal to the product of speed (v) and density (D). When density is examined, it can be described as the number of vehicles per unit length of roadway, while speed is the distance traveled per unit time.

Therefore, rewriting the classic flow equation q = v x D can help clarify that when we express speed in terms of density and space mean speed, the equation adjusts accordingly to v = D / S. This accurately demonstrates how speed decreases as density increases under uninterrupted flow conditions.

Making sense of this equation is crucial in understanding how traffic parameters interact. An increase in vehicle density on a roadway typically leads to a decrease in speed, which is essential when considering measures to improve traffic flow and enhance overall transportation efficiency.