The Highways Agency (HA) monitors the levels of skid resistance on its network using SCRIM survey machines. These machines measure skid resistance by running a wetted test wheel at an angle to the direction of travel and recording the forces generated. The levels of friction generated decrease as speeds increase. Therefore, a method of speed correction to a standard test speed has to be applied to allow different tests to be compared on a like for like basis. Different forms of speed correction have been applied to the SCRIM survey data over the years with each approach refining upon the previous. Recent work has found that the current speed correction equation (detailed in HD28/04) would benefit from further refinement. This report discusses the development of a new SCRIM speed correction formula.

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