Quantitative Safety Assessment of Vehicular Ad-hoc Networks (VANETs) in Freeway Traffic

Increasing population growth on the one hand and the growth of transportation industry on the other have had numerous positive and negative impacts in societies. This issue has led to an increase in the volume of traffic demand in road networks and has hence increased the number of road accidents. Research shows that a large number of accidents are caused by the human factor and the vehicle factor. By using vehicle-to-vehicle communication systems and turning static conditions (off-line) into dynamic conditions (on-line), the present study attempts to turn the human factor and the vehicle factor into the intelligent human and the intelligent vehicle, respectively, and reduce their effects on the occurrence of accidents. According to Statistics, a significant percentage of freeway accidents are rear-end crashes, in which human error has the greatest effects on such collisions. Although it is obvious that the use of such communication technologies enhances the safety level of roads, the quantitative and analytical insights of the increase of safety resulting from the use of VANETs in freeways has not been investigated yet. This study offers a new method for investigating the role of vehicular ad-hoc networks (VANETs) in reducing the number of front-to-rear accidents in freeways by reducing drivers’ reaction time. In so doing, by using the micro data of the traffic flow in the I-80 freeway of the NGSIM project, drivers’ behavior in a specific time span was analyzed; and by using indices of assessment of safety of emergency breaking (UDM), the safety of drivers at each moment was investigated. The results of data analysis reveal that the use of VANET communication networks can reduce the percentage of vehicles’ exposure to danger in the chase process from 68% to 15% by reducing drivers’ reaction time.