Supporting Drivers in Keeping Safe Speed in Adverse Weather Conditions by Mitigating the Risk Level

Overspeeding is both a cause and an aggravation factor of traffic accidents. Consequently, much effort is devoted to limiting overspeeding and, consequently, to increasing the safety of road networks. In this paper, a novel approach to computing a safe speed profile to be used in an adaptive intelligent speed adaptation (ISA) system is proposed. The method presents two main novelties. First, the 85th percentile of observed speeds (V85), estimated along a road section, is used as a reference speed, which is practiced and practicable in ideal conditions. Second, this reference speed is modulated in adverse weather conditions to account for reduced friction and reduced visibility distance. The risk is thus mitigated by modulating the potential severity of crashes by means of a generic scenario of accidents. Within this scenario, the difference in speed that should be applied in adverse conditions is estimated so that the highway risk is the same as in ideal conditions. The system has been tested on actual data collected on a French secondary road and implemented on a test track and a fleet of vehicles. The performed tests and the experiments of acceptability show a great interest for the deployment of such a system.