Investigation of Speed Cameras’ Effects on Road Network Safety by Using Time Series(Case Study: Tabriz - Zanjan Freeway)

Traffic safety issues due to speed increase accompanied by the rapid development of freeway and highway systems have increased the concern of the people and transportation policymakers. Speed limitation, as one of the most common safety measures, plays a unique role in protecting passenger safety. Thus, the study of traffic control effect by applying the speed limit on roads (especially freeways and highways) is scientifically significant to ensure passenger safety and functional performance. In this paper, by using time series method, road accidents in Tabriz-Zanjan freeway in design year (presence date of the speed cameras) have been predicted. Then by comparing the anticipated results with the real data, the impact of speed cameras on this road has been investigated. Before the modeling process, data collection, recording, framing and normalization operations were performed by Excel software and IBM SPSS software was used to construct the time series model. After comparing design year's data and examining the impact of cameras on this freeway, the number of fatal accidents decreased by 76%. The impact of speed cameras in reducing the number of crashes was negligible by 5%, and it did not have a positive impact on the number of injuries, and injuries increased by 38% this year. by investigation of available data from base year until horizon year, it was observed that upgrading road safety has been possible by adding appropriate designs and the speed cameras on this route have had an acceptable performance, and all three parameters (number of crashes, deceases, and injuries) have gone through a decreasing trend.