pervious surfacings act as a drainage layer , removing free surface water during rainfall, thus virtually eliminating the splash and spray thrown up by vehicles travelling on wet roads. however such surfacings compact under heavy traffic and the voids silt up reducing the effectiveness of the surfacings in preventing spray. six experimental open-textured bitumen macadam pervious surfacings having a high void content were laid in june 1970 on a worn rolled asphalt surface on the heavily trafficked trunk road a45 at stonebridge, warwickshire. harder binders than normal were used with two aggregate gradings to increase the effective life of the spray-reducing surfacings. details are given of the materials used, the mixing and laying procedure, the analyses of the mixed materials and the viscosity measurements of the binders before and after mixing. permeability values and percentage air voids are given for cores cut from the six different materials before trafficking and at subsequent intervals. values of the texture depth and the sideways force coefficient for each material are also given. the surfacings after two-years trafficking, including two and three quarter million commercial vehicles, are all in very good condition and still effective in reducing splash and spray. (a).

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