Analysing speed profiles for the estimation of speed on traffic-calmed streets

This research examines the speed profiles of individual vehicles on traffic-calmed streets in Christchurch, New Zealand, to provide a better understanding of how drivers react to calming devices over an extended street length and to find ways of estimating speeds along such streets. The results indicate that traffic-calmed streets do not necessarily promote low speed environments. It was found that 85th percentile speeds at long distances from calming devices were 45-55 km/h for horizontally deflected streets and 40-45 km/h for vertically deflected streets. The speed hump and the angled slow point produced the biggest speed reductions, while the 2-way mid-block narrowings caused no significant speed changes. The results also show that drivers have different perceptions of the appropriate operating speed at such devices, as evidenced by variations in speeds at the devices. Standard deviations in speed at speed humps and raised angled slow points were smaller than those at speed tables. For multiple devices, larger spacings produced higher speeds between devices. These findings, along with speed-difference relationships and speed-spacing models developed from this research, can aid in the selection of device type and spacing between devices, to improve the effectiveness of traffic calming.