Evaluation of speed indicator display as a traffic calming measure

Variable-message signs (VMS) are traffic control devices providing drivers with information along their way. In view of emerging conditions such as the increasing social role of inter-city routes, formation of small communities along them, and the high speed of vehicles in these areas that deteriorates safety, this study aims to use a special type of variable-message sign to help reduce the speed of vehicles on a key road in the Iranian Mazandaran Province. In this study, using affordable and compatible speed sensors, the speed of vehicles was recorded before and after the installation of the variable-message sign, to measure its effect on the speed, using special speed sensors. The device was equipped with infrared speed sensors (PIRs), wirelessly connected to the sign using IOT technology, and the speed of passing vehicles is detected by these sensors, and displayed online on the variable-message sign screen. The effect of the variable-message sign was measured using the average speed, the 85th percentile speed, and the speed of vehicles in different distances, i.e. 50 m, 30 m, 20 m before the sign, on the VMS, 20 m and 50 m after the sign. The results showed a 7% decrease in the average speed of vehicles in general; and respectively 6.5%, 11%, 11.3%, 3.7%, 6.3%, and 5.3% decrease at 50 m, 30 m, and 20 m before the sign, on the VMS, 20 m and 50 m after the sign, compared to the speeds recorded before the installation of the sign. Moreover, the 85th percentile speed at 20 m, 30 m, 50 m before the sign, on the VMS, 20 m and 50 m after the sign decrease 6, 7, 7, 4, 3, 3, 3 km/h respectively.