Speed-Based Design of Traffic Calming Schemes

Abstract. The objective of speed management (“traffic calming”) techniques used in neighbourhood traffic management is to change the speed profile in local streets so that it does not exceed target street speeds at any point. This paper outlines a suggested process for doing this, employing the concept of maximum “speed differential”, which signifies the severity of speed reduction expected at the location where a speed control device is to be installed. The process essentially involves three stages: measuring (or estimating) current free speeds; specifying the target street speed (thus identifying the required speed change); and designing a device or sequence of devices that achieve the target street speed while complying with the limit set on the speed differential at each device site. This requires a knowledge of the expected speeds at each device, and the typical approach and departure speed profiles. Information on both of these items needs to be collated and more widely exchanged between practitioners. The suggested process, originally conceived for inclusion in the new Australian guide for local area traffic management, offers guidelines for decisions on device spacings and isolated treatments.