The actual thickness of the film of water depends on the physic and morphologic characteristics of the paving (drainage conglomerate is usefully employed) as well as on the hydraulic conditions of the runoff. The transversal road grade is generally assumed to be a parameter sufficient to obtain a quick runoff of rainwater and, consequently, a moderate thickness of the film of water. However, the transversal slope of the platform is not influenced by the longitudinal road grade only when the plot is rectilinear. The effects of combined slopes in presence of easement or circular curves is not generally taken into account. In the present paper the results of a rigorous study concerning these problems is presented. concerning these problems is presented. The conditions which regulate the surface runoff of rainwater and the thickness of the film of water have been related to the overall geometry of the road plot and its grade. A computer program has been developed in order to evaluate the degree of safety of the road surface at the design stage. By means of the procedure it is also possible to locate the critical areas of the platform in case of exceptional rainfalls. This enables the adaption of adequate precautions both at design and running stage.
Abstract