LONG LIFE PAVEMENTS

The road pavement design charts used in the UK, like most of those in use throughout the world, involved considerable extrapolation of the results of full-scale trials to much higher traffic levels than experienced in the past. If this extrapolation is not accurate then resources may be wasted in the future. It was therefore important to examine the accuracy of this extrapolation. The performance of heavily trafficked roads in the UK was investigated, especially structural deformation, fatigue in the asphalt surfacings and the nature of the observed surface cracking. The results were surprising and showed that some of our traditional ideas about road behaviour needed to be fundamentally revised. They showed that traditional structural deterioration is very rare on the principal trunk roads of the UK and that most of the repair and maintenance works that are required are concerned solely with the surfacing. New road pavement design charts have been developed which place an upper limit on pavement thicknesses when roads are sufficiently strong to meet the criteria established for long life behaviour. The research also showed how to identify long life pavements and developed new assessment procedures to determine their maintenance requirements. The research had a significant impact on the asphalt industry which has concentrated, in recent years, on developing high quality thin surfacings with the primary aim of satisfying the functional requirements such as appropriate skid resistance, low noise properties, reduced spray in wet weather. (A)