Designing fail-safe and traffic efficient 802.11p-based rear-end collision avoidance

An essential, but nevertheless often neglected, objective for the design of safety-critical IEEE 802.11p-based application is: fail-safety. A fail-safe application is an application that incorporates features that automatically counteract the effect of anticipated sources of failure. In the context of a rear-end collision avoidance application two main possible sources of failure exist: an unpredictable human behavior and unreliable communication. This paper presents mechanisms that, when integrated into the design of rear-end collision avoidance application, counteract these failure cases and thus ensure fail-safety. However, fail-safety comes at a cost: either large inter-vehicle distances have to be kept to ensure that all drivers have enough time to react or the application has to take over vehicle control to allow smaller inter-vehicle distances and thus higher traffic efficiency. In this paper we analyze this tradeoff and quantify what part of drivers´ population has to be deprived of vehicle control in order to achieve acceptable traffic efficiency when deploying IEEE 802.11p-based rear-end collision avoidance application.