3.3 Traffic Headway Distributions
Prior to discussing different models for headway distributions, it is observed that, conventionally, a headway between two consecutive vehicles is associated with the trailing vehicle. In other words, the headway for any vehicle is considered to be its time separation from the vehicle immediately ahead of it, rather than from the vehicle immediately behind (see, for example, Akcelik et al. 1999). Of course, this time separation is between the times at which the same point on each vehicle (typically the front) passes a given location on the road.