The Road Note 31 is based primarily on the experience of TRL and collaborating organisations in over 30 tropical and sub-tropical countries. The majority of this experience has been gained in carrying out a research and development programme on behalf of the Overseas Development Administration but has been supplemented, where necessary, by additional projects for other aid agencies. The 4th edition extends the design of previous editions to cater for traffic up to 30 million equivalent standard axles. It takes account of the effects of climate and high axle loads, the variability in material properties and construction control, the uncertainty in traffic forecasts and the overall statistical variability in road performance. The range of structures has been expanded and the chapters on the different types of materials have been enlarged to provide more detailed advice on specifications and techniques. (A)
Abstract