Impact of Emergency Vehicle Preemption on Signalized Corridor Operation: An Evaluation

A case study that examines the impact of emergency vehicle preemption on closely spaced arterial traffic signals is reported. The study was conducted on State Route (SR) 26, a principal arterial and main thoroughfare that connects Interstate 65 with US-52 on the east side of Lafayette, Indiana. Four coordinated intersections along SR-26 were examined by using seven preemption paths and three different transition algorithms (smooth, add, and dwell). The number of preemption calls in the simulation period varied from one to three for equal simulation periods. The findings generally show that a single preemption call had a 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 the 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 on arterial travel time observed was an increase in the average arterial travel time on the order of 20 to 30 s. The study focused on emergency vehicle preemption, but the general procedures described could also be applied to railroad preemption or transit priority.