In order to assess the performance of asphalt surface courses laid on the trunk road network, the Scottish Inspection Panel (SIP) assess the visual condition of a selection of surface courses each year. The results are gauged against previous surveys of materials of a similar age. The survey team also record any features that appear to affect the long-term performance of the surface course to establish initial causes and typical modes of failure. In addition, older sites are assessed to estimate the typical service life of a surface course. The latter is required for asset management purposes, life-cycle planning and demonstrating value for money. Based on the observations and results of the SIP surveys, several recommendations are made to improve material design, construction and aftercare. Future visual inspections are suggested as they provide the mechanism to drive continuous improvements in the performance of surface courses.

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