This report describes the development of a method for detecting and describing edge deterioration on local roads. This work has been carried in order to assist the DfT in its goal of introducing TRACS Type Surveys (TTS) on the non-Principal Road Network. These surveys are scheduled to begin in April 2005. Existing TTS machines and survey methodologies do not provide any measurement of edge deterioration as they have been developed for principal roads, where such defects rarely occur. Edge deterioration has been found to be one of the main causes of maintenance of local roads, and as such it is very important that it can be detected reliably. TRL was therefore commissioned to develop appropriate techniques for detecting and describing edge deterioration on local roads. The timescale for implementation of any methods developed for detecting edge deterioration was very short, and it would be impossible to make any modifications to the survey vehicles in the time available. Therefore any new methods developed had to operate successfully using data already collected during TTS surveys. Three methods were developed which meet the requirements of the DfT and the Local Authorities. These methods all make use of transverse profile measurements as currently provided using machines meeting the TTS specification. Improved processing techniques allow information relating to edge condition to be derived. The first of these methods looks at the edge roughness of the road. This looks for changes in the short wavelength longitudinal profile variance at the edge of the road. The second method measures the magnitude of any step down at the edge of the road, from the road to the verge. The third method compares the transverse profile variance in the nearside of the transverse profile, with that in the offside of the same profile. The methods were developed and tested on a selection of local roads, and it has been shown that the outputs of the process can be related to the presence of edge deterioration as reported during visual inspections. The report describes the methods which were developed, and makes recommendations for their implementation, and considers the implications of the work on the wider goal of introducing TTS on local roads. (A)

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