The paper reports the frame, methods and findings of a study assuming that non human factors, such as specific combinations of route and environment layouts, might take part in the magnitude of speed offending observed in France in small 50km/h areas located on rural roads. Speed controls being 2 times more frequent in small sites and not curbing high speeding rates (70% of infringement) and related cost in fatal accidents (18% extra), required knowing what interfered with the 50km/h police enforcement. Noticing that electing/adjusting the route speed actually relies at first on the visual dynamic perception of route facilities and constraints, local route and surroundings designs were suspected to induce speed facilities counteracting the 50km/h limitation. Checking this eventual impact required first describing site crossing, then evaluating the relationship between site crossing and site speed average already available. It was realised with the building of a specific method of site description relying on the visual perception of site crossing when coming from open roads. Sequential pictures and measurements were taken for this purpose in 75 small sites. Besides evidence of route configurations acting against the 50km/h enforcement and discrediting the legitimacy of speed limitation and police control, the method used in the study provides additional tools for improving enforcement. Patterns of crossing characteristics having an evident speed influence can be used for diagnosing sites contributing to speeding and for processing to changes in route configuration so as to make the crossing consistent with the 50km/h limitation. For the covering abstract see ITRD E123863.
Abstract