What does the fundamental law of traffic flow state?

The fundamental law of traffic flow states that flow is equal to density multiplied by speed. This relationship indicates that the amount of traffic passing a given point over time (flow) is dependent on both the number of vehicles occupying a section of roadway (density) and how fast those vehicles are moving (speed).

In practical terms, if you increase the density of vehicles on a roadway while maintaining a speed, the overall flow of traffic will increase. Conversely, if the speed decreases while the density remains constant, the flow will also decrease. This principle is crucial for understanding traffic dynamics, especially in planning and managing roadways to optimize traffic efficiency and reduce congestion.