Abstract
Vehicular time headway is an important parameter which characterizes traffic flows and a great number of Road Engineering applications utilize timeheadway statistical models. Two dichotomic laws are presented: these distributions can be useful in studying partially conditioned flows. Then, a complete method for the calibration of these models, which is alternative to the moments method, is given. Finally, a comparative analysis is made between the proposed models and others available in literature on the basis of a common significant set of measured time headways.