Two Vehicular Headways Time Dichotomic Models

Vehicular time headway is an important parameter which characterises traffic flows and a great number of Road Engineering applications utilise time headway statistical models (for example the distribution of time headways contributes to the determination of the capacity, delay and queue at intersection). In this paper two dichotomic laws are presented: the log-normal shifted negative exponential distribution (ENTLN) and the Pearson’s type III shifted negative exponential distribution (ENTPIII). These distributions can be useful in studying partially conditioned flows. A complete method for the calibration of these models is then given and is an alternative to the method of moments. Finally, a comparative analysis is made between the two models proposed and others available in literature on the basis of a common significant set of measured time headways.