Research at the UK Road Research Laboratory showed a significant relationship between polishing of aggregates used in road surfaces and skid resistance. Tests were devised using an Accelerated Polishing Machine and a friction measuring device, Portable Skid Resistance Tester, to determine a Polished Stone Value.

    
These developments have resulted in a simple and inexpensive procedure to determine in advance of a road being built what its resistance to skidding will be.

The Accelerated Polishing Machine was first produced 25 years ago. Today, more than 1000 of these machines have been supplied world wide to Materials Laboratories, Consulting Engineers and Research Institutions.

The action of road vehicle tyres on road surfaces results in polishing of the top, exposed aggregate surface, and its state of polish is one of the main factors affecting the resistance to skidding.

Resistance to this polishing action is determined principally by the inherent qualities of the aggregate itself. A later section of this memorandum gives some information about the polishing resistant qualities of different sources of aggregate.

The actual relationship between PSV and skidding resistance will vary with traffic conditions, type of surfacing and other factors. All factors together with reproducibility of the test should be taken into account when drawing up specifications for road works, which, include test limits for PSV.

The PSV test is carried out in two stages - accelerated polishing of test specimens followed by measurement of their state of polish by a friction test.