Helping to lower accident rates by identifying where there is a risk of wet-road skidding.
Since the mid-70s highway authorities have used the SCRIM® road survey machine to indicate those lengths of road where the skid resistance is below investigatory levels.**
The standards are based on over 30 years of research and have been shown to correlate strongly with the excessive risk of wet road skidding accidents.
Recent studies in England, Scotland, Wales and New Zealand have confirmed that the current standards published in 2004 are highly cost effective as well as appropriate to current traffic flows, road conditions and materials.
Studies in both the United Kingdom and in New Zealand show that introducing a wet road skidding policy will reduce accidents by between 30 and 40% over and above the results of other safety improvement programmes.
The introduction of regular SCRIM machine surveys, together with a skid policy based on the current standards, offers a very cost effective option for local authorities to achieve and maintain reductions in their road casualty rates.
The SCRIM machine survey is applicable to all surfaced roads where the volume of traffic justifies its use and where the equipment, which is lorry based, can travel safely at 50 km/hr.
The results from SCRIM surveys identify those locations where the skid resistance is below investigatory levels and relate to the risk of an accident.
The concept behind the standards is that there should be a uniform risk of a wet road skidding accident across the whole network.
The lowest skid resistant aggregates are required on dual carriageways away from junction areas while the highest standards are required on the approaches to roundabouts and pedestrian crossings. This approach provides a sustainable policy by targeting the best aggregates to the highest risk areas.
Management of the safety of a network and the control of wet road skidding accidents can be achieved only if the skid resistance of the network is known and those measurements can be related to national standards.
With knowledge of skid resistance, investigation of deficient sites can be undertaken to help reduce accidents, provide continuous improvement in the accident rate and obtain best value.
* SCRIM is the registered trade mark of W.D.M. Limited
** Published in the Design Manual for Roads and Bridges and in the Local Authorities Code of Practice