RESEARCH ON LIGHTLY TRAFFICKED URBAN AND RURAL ROADS

A review is made of some ARRB research projects, on pavement materials and design, which are related to the behaviour of lightly trafficked urban and rural roads. The projects are those with which the author has been either directly or indirectly involved. For pavements in the residential areas surveyed, the subgrade had attained near saturation, and seasonal movements of moisture were shown to be small and to occur only at the pavement edge. Overall strength measurements as indicated by Benkelman beam testing are proposed for determining maintenance procedures. A survey of the vehicle population provided data on critical dimensions for cross-overs and field testing of gutter inlets led to modifications of earlier recommendations. For pavements surveyed in the rural areas subgrades attained an equilibrium moisture condition of generally less than 0.90 of standard optimum moisture content. Along the coastal strip subgrades are likely to become wet of standard optimum moisture content. For these conditions, full width construction is preferred to boxed construction. "Dry" compaction, of road making is possible, but heavy compaction equipment is necessary for the best results. In the wet tropical areas, significant seasonal subgrade moisture change can occur under the whole of the road. (TRRL)