A stochastic approach for vehicle safety modeling in a platoon of vehicles equipped with vehicular communications

Among the safety-related applications of vehicular ad hoc networks (VANETs), the Cooperative/Chain Collision Avoidance (CCA) techniques have received special attention in recent years. With CCA systems a fast dissemination of warning messages to the vehicles in the platoon enables them to promptly react in emergency situations. In this way the number of car accidents and the associated damage to drivers and passengers can be significantly reduced. These systems are usually evaluated through simulation. However, to cope with the drawbacks of simulating accidents with current tools based on car-following characterizations, we propose the use of a stochastic model as an alternative to simulation for the design and evaluation of such applications. The model allows the computation of the average number of collisions that occur in a platoon of vehicles, the probabilities of the different ways in which the collisions may take place, as well as other statistics of interest. As shown in this paper, the model enables the evaluation of different scenarios and communication technologies, characterized by using the appropriate distributions for its parameters. The main practical utility of this approach lays on its ability to quickly assess numerically the influence of different parameters on the collision process without the need to resort to complex simulations at a first stage. Such an evaluation provides relevant guidelines for the design of vehicular communication systems. To exemplify it, we provide an evaluation of different types of CCA applications in two scenarios, a freeway and an urban scenario.