Effect of Traffic Calming Measures Implemented on the Approach to the Tempo–30 zone on the Degree of Speed Reduction

Abstract

Tempo–30 zones are implemented primarily to calm the traffic by reducing the operating speed to the desired level of 30 km/h. To this end, various traffic calming measures are installed. With the purpose to determine the traffic calming measures that are the most effective in terms of speed reduction speed measurements were conducted on a few chosen Tempo–30 zone approach sections containing various traffic calming measures: traffic circles, raised junctions, speed tables, speed bumps/humps and horizontal deflections on raised junctions. Another factor differentiating the sections chosen for the research was the Tempo–30 zone entry feature, such as a mini roundabout or a simple or signalled junction. The measurements were carried out under free-flow traffic conditions during peak hours. During all the measurements the weather was dry and such was the pavement surface. The 85th percentile speed v85 and the average speed were calculated. For simultaneous measurement on the respective measurement points P1, P2, … Pn SR4 electronic speed and traffic volume measuring systems equipped with automatic recording function were used. The measurement data were analysed and the results show that the obtained operating speeds were below 30 km/h (that is below the maximum permitted speed in Tempo–30 zone) only on a few sections. The most sustained speed reduction effect was obtained on two research sections containing several vertical traffic calming measures, including raised junctions, speed tables or speed bumps/humps. The effectiveness in speed reduction was ascertained for combined use of different traffic calming measures imposing vertical and horizontal deflections of the vehicle paths of travel. However, the most effective arrangement was a series of vertical traffic calming measures provided on the Tempo–30 approach section. Conversely, a mini roundabout, traffic circle or signalised junction at the entry to the Tempo–30 zone had only a minor speed-reducing effect. The same applies to repeated small horizontal deflections on the approaches to raised junctions.