Speed is inversely correlated with which other major traffic stream parameter?

Speed is inversely correlated with density in traffic flow dynamics. This relationship is grounded in the fundamental principles of traffic theory, often illustrated by the fundamental diagram of traffic flow.

As the density of vehicles on a roadway increases, the available space for each vehicle decreases, leading to reduced speed. When more vehicles occupy a given length of road (high density), they naturally have less room to maneuver and may need to slow down, resulting in lower speeds. This inverse relationship highlights how traffic conditions can shift; at high densities, the speed tends to drop significantly due to congestion.

In contrast, when density is low, vehicles can move more freely, which typically results in higher speeds. Understanding this relationship is crucial for traffic engineering and management as it can aid in predicting congestion and optimizing traffic flow.

The other choices—flow, capacity, and volume—are related but do not describe the same inverse correlation as density does. For instance, flow represents the amount of traffic passing a point in a given period, whereas capacity refers to the maximum flow a roadway can accommodate under optimal conditions. Volume indicates the total number of vehicles over a particular time but does not directly illustrate the inverse relationship with speed as density does.