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Road Safety and Polished Stone Values
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The fundamental purpose of the Polished Stone Value is to enable safer roads to be built. In the UK use of PSVs in road construction has had a major influence in reduction of accidents. The following is an interesting example.

Elevated section of M4 experiment


This site, the elevated part of Motorway M4, was found to have a high proportion of skidding accidents when wet. Examination of the records showed that the SFC (Sideways Force Coefficient) of the surface was from 0.35 to 0.45 at 50 km/hr. The road was resurfaced with the highest PSV material available at the time. It had been intended to use calcined bauxite (RASC Grade) for the entire site, but as insufficient material was available, it was decided to mix it with a gritstone from Gilfach quarry near Neath, in South Wales, with a PSV of 71.


During the first three years after resurfacing the SFC was found to have increased to between 0.50 and 0.60 and accidents were substantially reduced.