Impact Evaluation of Emergency Vehicle Preemption on Signalized Corridor Operation

This study reports on a case study examining the impact of emergency vehicle preemption on closely spaced arterial traffic signals. The study was conducted on SR 26 a principal arterial and main thoroughfare connecting Interstate 65 with US 52 on the East side of Lafayette, Indiana. This study examined four coordinated intersections along SR 26 using seven preemption paths and three different transition algorithms (smooth, add, and dwell). The number of preempts in the simulation period varied from one to three preempts for equal simulation periods. The findings generally show that a single preemption call had minimal effect on the overall travel time and delay through the network. The results also indicate that the smooth transitioning algorithm performed the best with most scenarios and paths, for both the arterial and side streets. When multiple emergency vehicles preempt at closely spaced time intervals, the impact of preemption was more severe. For the network studied, the most severe impact observed on arterial travel time was an increase in the average arterial travel time on the order of 20-30 seconds. This study focused on emergency vehicle preemption but the general procedures described here could also be applied to railroad preemption or transit priority.