Evaluation of the Performance of VSL Signs for Safety Promotion in Rural Roads (Case Study: Haraz Road)

Providing the roads with safety equipments and standardization can be efficient in decreasing accidents. In this research, safety equipment, called variable speed sign, has been evaluated. This sign changes the speed limit according to the environmental and geometric conditions of the road and also traffic volume. By recognition of effective factors on the performance of variable speed signs and factors affecting the speed, appropriate variables related to this research are selected and used to develop a model based on the number of accidents. Such model is once built based on data found before installation of the variable speed sings and the model outcomes are compared with the model results based on accidents data obtained after installation of the signs. Several types of applicable models were studied using the accident data and for each case, required statistical tests were performed. Ultimately, negative binomial regression model was selected due to the advantages of the models. It was found that by installation of variable speed signs and precise control of the speed limit, reduction in accidents has been significant while installation of such signs has deemed to be economical.