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:
nveh = 3600s / Tmin
Where nveh denotes the vehicles per hour and Tmin denotes the minimum safe headway, in seconds.