Free-flow speed is defined in relation to what aspect of traffic flow?

Free-flow speed refers to the speed at which vehicles can operate on a roadway without significant interference or interruptions from other vehicles, traffic signals, or conditions that would impede their movement. This speed typically occurs in low-traffic conditions where drivers are able to maintain a smooth trajectory and consistent speed, unencumbered by congestion.

When discussing free-flow speed, it's important to note that it represents an ideal scenario where the roadway is not congested, and vehicles can move at their desired speeds according to speed limits and road conditions. This contrasts with situations experiencing congestion, where maximum speeds are limited by the density of traffic.

In essence, free-flow speed provides a benchmark for understanding traffic conditions and informs roadway design, signal timing, and congestion management strategies. It aids in assessing how effectively a roadway can handle traffic, as well as guiding decisions on safety and efficiency for roadway users.