SIGCOM3: a traffic signal optimization model for isolated intersections

Abstract

The need of updating the series of SIGCOM programs, now in its third version, is in accordance with the continuous improvements that any program has to have to be valid. Like its predecessors, SIGCOM 3 delivers the optimal cycle length and the optimal green time split for an isolated intersection controlled by a traffic light. The objective function in the optimization process is selected by the user among multiple options that the program offers as performance indicators. As a first approach, the work done by von Mühlenbrock (2005) was revised, to corroborate the important progress contributed, on one side, by incorporating studies done in Chile on estimating capacity and prediction models of lane selection, as well as writing this program in Visual Basic.Net, which offers a much more friendly interface with the user. The most commonly used performance indicators for measuring a intersection are the number of stops, the delays and a combination of the two. In this version of SIGCOM, the expressions that measure these indicators have been modified, replacing Allsop formulas (1971) by Akcelik formulas (1981). The expressions found by Akcelik work even under high level of traffic demand, which was a limitation in the first two versions of this program. The above mentioned Akcelik formulas (1981) for the number of stops and delay consider a term which includes the length of the overflow queue, which corresponds to the number of vehicles that stay at the intersection after a green light has finished. This concept was studied in depth in this study and a correction was made in the way this value was interpreted and calculated. Undoubtedly, this constitutes the most relevant contribution of this study. In conclusion, SIGCOM 3 delivers an improved version of this saga, in which the greater versatility and the online help grant a much better experience for the end user.