TRRL LR 1050
An unconventional pavement design, in which a well compacted upper roadbase of dense bitumen macadam is placed between hot-rolled asphalt wearing course and lower roadbase, has been developed. This new design meets recent requirements for design lives for traffic loading equivalent to 150 million standard axles, well above the limit of present design specifications. Using an analytical method developed at TRRL, the design was predicted to have a fatigue life five times that of a conventional structure of the same thickness. Compared with this factor, the sensitivity of the analytical design method to realistic variation in input parameters was low. The new design incorporates features which should ensure a resistance to permanent deformation at least as good as that of conventional designs produced by a simple extrapolation of current design standards. The analytical method realistically estimated the fatigue resistance of a full-scale experimental pavement. Further validation is sought. The choice of the new design for the reconstruction of a heavily trafficked section of the M6 is discussed. Designs suitable for traffic in the range 80 to 250 msa are given