Impact of Police Enforcement on Critical Gap at Roundabouts

Abstract

At modern roundabouts, entering vehicles must yield right of way to vehicles in the circulating lane and can only proceed if there is a proper gap. The critical gap is the minimum acceptable gap that a driver will use to enter the roundabout. It is thus assumed that drivers will reject gaps of a value less than it and will accept gaps of a value more than it. In some countries, due to heavy congestion, police enforcement officers monitor and regulate the movement of vehicles at critical roundabouts during the peak hours of the day as needed. In some cases, police enforcement officers will be present at the roundabout during peak hours without interfering with the traffic flow to reduce the incidence of traffic violations. The purpose of this study was to investigate if there is a change in driver behavior in the form of a change in the critical gap value. A major roundabout was used to investigate the effect of police enforcement presence. The results of the study indicated that the critical gap during the police enforcement presence was 2.13 s whereas the critical gap of the roundabout during normal conditions was 2.42 s. The reduction in the critical gap is an indication that roundabouts can perform better and handle more traffic volume when police officers are present.