Two-Stage Gap Acceptance: Some Clarifications

Chapter 17 of the Highway Capacity Manual (HCM) 2000 provides a method for analyzing a two-stage priority process at unsignalized intersections, which provide a wide median in the major street. In the HCM itself, the method is described rather briefly. This briefness could give rise to misunderstanding, and practitioners might avoid using the procedure altogether. Therefore, the analytical background of the procedure and the correct application of the parameters are explained in greater detail. Moreover, graphical representations have been developed to replace the difficult formulas, significantly simplifying application in the field. The method also has some limitations, which should be taken into account in practical application. Thus, this paper is something like a comment on the method described in the HCM 2000, besides providing some enhancements that allow easier application in practice.