Fretting of road surfaces is becoming a defect of increasing concern for road authorities throughout Scotland. However, current analysis of condition survey data does not include indicators to identify locations that are affected by fretting, making scheme identification and programming challenging.

It has been observed that fretting can be associated with higher levels of texture reported in the SCANNER survey. Therefore an investigation into the use of texture data to provide an indicator of fretting has been carried out.

Assessment of the relationship between the existing SCANNER parameters and the results of VCS surveys led to the conclusion that there is little agreement between the current SCANNER texture parameters (SMTD, MPD, RMST) and fretting reported in the VCS. Thus these parameters cannot be used to identify fretting reliably on Scottish trunk roads.

Raw Condition Data (RCD) provided by the SCANNER survey has also been used to investigate the application of an algorithm developed in the Highways England TRACS survey specifically for the measurement of fretting. This parameter has shown more potential, but the results are complex. An initial assessment shows a reasonably low level of true positive, but several false positive reports of fretting. However, analysis shows that there are valid reasons for the false positives, many of which are associated with the reporting of features that are not fretting, but are defects. The algorithm is also constrained by the low level of resolution available in the texture data in comparison with the levels upon which the algorithm was developed. The work has therefore concluded that there is a need for the work to continue, to obtain a more complete understanding of the potential capability of this approach in assessing fretting on Scottish trunk roads.

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