Citation

Teng H, Kwigizile V, Xie G, Kaseko M, Gibby A. J. Transp. Res. Forum 2010; 49(1): 69-79.

Copyright

(Copyright © 2010, Transportation Research Forum)

DOI

unavailable

PMID

unavailable

Abstract

Emergency vehicle signal preemption allows emergency vehicles to pass through intersections quickly and safely. However, signal preemption interrupts regular traffic signal operations and it may take a significant amount of time for traffic signals to transition back to normal operations after a preemption. This paper uses global positioning system (GPS) data from paratransit vehicles in Las Vegas, Nevada to evaluate the impact of emergency vehicles on urban traffic speeds. The GPS data were used to derive speed and travel time data for roadway segments where paratransit vehicles traveled. The results indicate that speed variance is significantly higher during emergency preemption and the mean speeds of traffic flowing in the same direction as the emergency vehicle and on crossing streets are lower during preemption than during normal conditions. Regression results indicate that traffic on major arterials and traffic in the opposite direction of the emergency vehicle tend to have higher speed during signal preemption. Signal preemption during peak periods and duration of preemption had a significant negative impact on traffic speeds. Transition time also had a negative impact on traffic speeds.