Published: Jan 1990
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Research associated with skidding resistance has been ongoing at the Transport and Road Research Laboratory (TRRL) for over 50 years, and in 1979 a draft “Standard” based on that research was prepared by the Department of Transport for implementation on the National trunk road network. However, the Standard was not issued because not enough was known about the existing levels of skidding resistance, and with the information then available it was not possible to demonstrate the cost-effectiveness of introducing the policy.
In an effort to provide the necessary information, the Department planned a National Skidding Resistance Survey (NSRS) based on the Sideway-force Coefficient Routine Investigation Machine (SCRIM), and during 1982 survey was undertaken on a short (approximately 10-km lengths) sample basis to represent the network nationwide and to provide an adequate number of samples of the many different categories of site that are encountered on a road system. Altogether a representative sample of about 1000 km was taken forward for further analysis. The sample was broken down into short subsections and each allocated to a site category such as traffic light approach, nonevent open road, motorway, bend, major junction, minor junction, dual carriageway, and single carriageway. Average and minimum skidding-resistance values were determined for each subsection and all injury accidents, each defined by type (dry no-skid, dry skid, wet no-skid, wet skid), were allocated to the subsection of their occurrence.
Analysis of the data demonstrated that very different skidding resistance/accident relationships existed between the various categories of site. Based on the findings, a policy was developed that would not only save accidents but also could be shown to be highly cost-effective. The paper briefly summarizes the findings of the NSRS and outlines the general principles (including skidding resistance values) of new skidding-resistance policy for in-service roads.
skidding resistance, policy, standards, in-service roads, SCRIM, seasonal variation, skidding-resistance investigation
Engineer, Transport and Road Research Laboratory, Crowthorne, Berkshire