What formula represents the relationship between density, flow volume, and space mean speed?

The correct formula indicating the relationship between density, flow volume, and space mean speed is derived from fundamental traffic flow theory. Density is defined as the number of vehicles per unit length of roadway. Flow volume refers to the total number of vehicles passing a point over a given time period, while space mean speed is the average speed of vehicles on a segment of road in terms of the distance traveled over the time taken.

The relationship can be expressed mathematically as follows:

Density is equal to the flow volume divided by the space mean speed. This is because when flow volume is high and space mean speed is relatively low, the density increases, meaning more vehicles occupy the same length of road. Conversely, if space mean speed increases, the same volume of vehicles will occupy less space, leading to lower density.

This formula helps in understanding traffic performance and management, allowing engineers to analyze how changes in one variable (like flow volume or speed) can affect overall traffic density on roads.