The queue discharge problem at a signalized intersection was analyzed with application of the modified Pitt car-following system. The Pitt car-following system was implemented on an Excel spreadsheet in the form of a prototype simulation model. The situation consisted of a single intersection in which discharging vehicles were unconstrained by downstream conditions. It was asserted that the car-following parameters used in the queue discharge problem are significantly different from those used in the uninterrupted-flow problem and that this is consistent with the two-fluid model. A number of scenarios were executed for each situation, using the spreadsheet implementation to examine a number of issues, including the effect of the following: free-flow speed, car-following parameter variations, vehicle length, heterogeneous traffic streams, and lane changing. It was shown that all of these issues have significant effects on discharge headways and that the Pitt car-following system has a far wider range of applicability than the simple equal headway model. The intuitiveness of the findings and calibration and validation issues were also addressed.
Abstract