Could adherence and road geometry be used to identify the areas of risk?

Michel Gothie

Although road traffic accidents rarely have a single cause, if we take into account the relative amounts of time pavements are wet rather than dry, twice the proportion of accidents occur on wet pavements. This paper uses a number of case studies to attempt to assess if adherence and road geometry could explain the increased risk during wet weather. In recent years, the link between pavement surface characteristics and accident risk on wet pavements has been demonstrated by a number of authors from different parts of the world. The analysis conducted in the studies described in this paper confirms this link, without claiming to measure in absolute terms the effect on road safety of the factor considered (friction, texture or layout). Nevertheless, comparisons between case studies on routes with very different layouts and driving conditions show that: 1) friction and texture characteristics have the same type of effects on the accident rate on wet pavement, namely - a) the accident rate tends to increase when the sideway force coefficient or the macrotexture diminishes, b) the change in the accident rate is not steady, but becomes much less below certain values; 2) the curvature radius of the bends, on difficult road layouts, is an important factor of influence on the accident rate, and on the severity of these accidents.



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