Free-Flow Speed is defined as which of the following?

Free-Flow Speed is defined as which of the following?

• A. Average speed during peak hours
• B. Speed limit under ideal conditions
• C. Free-flow speed occurs when density is high
• D. Speed of traffic when density is 0

Answer: (D)

Free-flow speed is the speed vehicles maintain when there are no other vehicles to interact with. In other words, it's the speed you’d observe under unconstrained conditions, when density is essentially zero and drivers aren’t impeded by following or being held up by others. This is why the best description is the speed of traffic when density is zero: there’s no congestion to slow trips down, so each driver travels at their preferred pace. This isn’t the same as the average speed during peak hours, which reflects congestion and slowdowns. It isn’t simply the posted speed limit under ideal conditions, since free-flow speed describes actual driving behavior under noVehicle interaction, which can differ from the limit. And it isn’t the speed at high density, where interactions slow traffic.

Free-flow speed is the speed vehicles maintain when there are no other vehicles to interact with. In other words, it's the speed you’d observe under unconstrained conditions, when density is essentially zero and drivers aren’t impeded by following or being held up by others. This is why the best description is the speed of traffic when density is zero: there’s no congestion to slow trips down, so each driver travels at their preferred pace.

This isn’t the same as the average speed during peak hours, which reflects congestion and slowdowns. It isn’t simply the posted speed limit under ideal conditions, since free-flow speed describes actual driving behavior under noVehicle interaction, which can differ from the limit. And it isn’t the speed at high density, where interactions slow traffic.