Letter to the Editor—Comments on “Car Following Headways on Freeways Interpreted by the Semi-Poisson Headway Distribution Model”

We are disturbed by some of the misleading remarks made about our work on the generalized queueing model (GQM) headway distribution by Paul Wasielewski in his recent Transportation Science paper “Car Following Headways on Freeways Interpreted by the Semi-Poisson Headway Distribution Model” (s-PM). It is clear to us from his references to our papers (Cowan, R. J. 1975. Useful headway models. Trans. Res.9 371–375 and Branston, D. 1976. Models of single lane time headway distributions. Trans. Sci.10 125–148.) that he had misunderstood the arguments employed in them. Because of this we feel that he misrepresents both our work and the physical basis of the GQM. We acknowledge that Wasielewski is entitled to promote the s-PM, but if he wishes to refer to our work, then he should do so without error. We are outlining some of the errors made by Wasielewski below.