Passing Parked Police Cars: Speed as a Function of Emergency Lighting, Police Car Orientation, and Driver Experience

Abstract

Police vehicles and police officers working on the roadway shoulder are at risk for being struck by passing vehicles. The conspicuity of police vehicles may affect detection and speed regulation. Fifteen novice and fifteen experienced drivers participated in six experimental sessions over six months with a moderate-fidelity driving simulator. Police cars were parked on the shoulder and oriented forward or backward with their emergency lights on or off. When the emergency lights were on, drivers slowed down more than when the lights were off. The orientation of the police vehicle had minimal effects on speed changes and novice and experienced drivers did not appreciably differ in their speed regulation. When compared to the criteria of reducing speed to 60 km/h when passing an emergency vehicle, which is the law in Alberta, only 16% of all drivers reduced their speed below this limit. Results suggest that drivers do not sufficiently reduce their speed in the presence of police cars and emergency vehicles should always use their emergency lights whenever they are parked on the side of the road.