Since 1994, TRL in collaboration with a number of road authorities and consultant partners has been engaged in extensive studies of the performance of low volume sealed roads within Southern Africa. The roads included in service primary and secondary roads with ages varying from thirty years old to relatively new roads and specially constructed experimental sections. The roads examined were located in Botswana, Malawi, Zambia and Zimbabwe. This paper contains a summary of the new materials specifications and design requirements for low volume sealed roads derived from studies in the region and describes the experimental design and performance of studies of secondary and feeder roads in Zimbabwe which have been crucial to the derivation of recommendations. The observed rates of deterioration on these roads are compared with those predicted by the Highway Development and Management tool HDM-4, in order to derive appropriate calibration factors for cracking, rutting and roughness progression models. These have then been applied in an economic evaluation to derive life-time costs of sealed roads built to different standards. (A)
Abstract