URBAN SPEED MANAGEMENT. 2. AUTOMATIC SPEED ENFORCEMENT

This is the second of two papers, dealing with the quantitative methods and understanding that are essential for developing speed management strategies for urban roads. For abstract of the first paper see IRRD 886840. The present paper is concerned with speed enforcement methods, such as speed cameras. It aims to develop simple behavioural models of speed setting, to contribute to the understanding of some of the more complex issues arising in speed management and enforcement. Drivers' choices in speed setting are modelled on their assumed trade-off between journey time and accident risk for a section of road. Research at the Transport Research Laboratory (TRL) found that speed cameras could effectively reduce 85 percentile speeds to their potential limit, allowing for vehicle class limit differences, and eliminate as far as possible the presence of 'fliers' travelling over 20mph above the speed limit. Fixed-site speed cameras can control speeds well in critical locations, where they can be operated relatively cheaply and simply. Mobile cameras can control vehicle speeds very well over large sections of the road network. Possibilities for automatic speed control are discussed briefly; this approach causes much less driver stress and discomfort than effective methods of traffic calming and automatic speed enforcement.