The report presents an international review of research and national practice in oecd member countries in the field of road strengthening. The first chapter highlights the importance of this problem and introduces the main factors when planning, designing and carrying out strengthening works. Chapter ii of the report defines the reasons for carrying out sound strengthening and outlines various options or strategies available on the road network and on individual roads. The economic evaluation of these strategies is considered in chapter iii. Systematic measurement is the key to the assessment of road condition at both the network and individual road level. The factors concerning the choice of measurements used for assessment at both levels and the way in which the measurements are processed and used to build up a picture of road condition are considered in chapter iv. The equipment available for assessing the condition of the road and providing the necessary input to methods for designing measures for structural strengthening is described in chapter v. Information about a wide variety of design methods has been published, some are under development, others are operational but few are systematically verified. Chapter vi describes the main types of method being used or developed in oecd countries, distinction being made between methods for strengthening flexible pavements, concrete pavements and semi-rigid pavements. The design of strengthening measures must take into account the constraints imposed by the layout and condition of the roads and the materials to be used. Some of the problems of translating design into practical reality are outlined in chapter vii. The group concluded that there remains a need for more rapid methods of measurements of structural road condition, for the development of new road materials for strengthening purposes and for a greater understanding of the role of soil strength in relation to road drainage as it affects strengthening. More information is also required on the relation between maintenance standards and the risk of premature deterioration and on user costs and benefits so that economically, rather than technically, based standards can be used. (A)
Abstract