Information Age in Forward Collision Warning Based on Vehicle-to-Vehicle Communications: Sensitivity Analysis

Connected vehicles transmit and receive basic safety messages that enable the use of safety applications intended to avoid crashes. The information age (IA) is the latency between the basic safety message being generated by the transmitting vehicle and received by another vehicle. The receiving vehicle's processing time is included in the IA but, at several milliseconds, can be ignored. The IA of vehicle-to-vehicle communications needs to be kept beneath a certain threshold so as not to compromise the effectiveness of safety applications. Forward collision warning (FCW) requires a critical IA in scenarios in which a lead vehicle brakes hard and abruptly. An analytical model of FCW, with the lead vehicle coming to a complete stop, is proposed. For the host vehicle behind the lead vehicle to stop safely, an appropriate IA, perception reaction time, and deceleration rate are required. Sensitivity analysis of the IA is performed to provide the probabilities of a safe stop for various combinations of speed and deceleration rate. Monte Carlo simulations are implemented to generate the probabilities, and perception reaction times, speeds, and deceleration rates are formulated as probability density functions. The results show that the IA is a sensitive factor in the safe operation of an FCW application. The IA for a low-speed host vehicle is more sensitive than the IA for a high-speed host, when the host and lead vehicles are both traveling at similar speeds with a normal clearance gap. The IA is more sensitive when the host vehicle speed is low (<= 40 mph) or when the lead vehicle's deceleration rate is high (>= 0.5 g).