What is Roadway Capacity?

The maximum sustainable hourly flow rate at which vehicles reasonably can be expected to traverse a point or a lane on a roadway during a given time period, typically 15-minute intervals under prevailing roadway, traffic, and control conditions. It is expressed in vehicles per hour per lane.

Capacity is often expressed in vehicles per hour and calculated as:

n_veh = 3600s / T_min

Where n_veh denotes the vehicles per hour and T_min denotes the minimum safe headway, in seconds.