REVIEW OF FLEXIBLE AND COMPOSITE PAVEMENT DESIGN METHODS

COST Action 333 aims to contribute to the development of a new design method for flexible and composite roads in Europe that will be based on the latest research findings and the latest developments in pavement modelling. This is a concerted European research action that is focused towards information gathering, identification of requirements and selection of design elements. Once this is achieved, it will be possible to develop the design elements and produce a coherent, cost-effective and harmonised pavement design method that can be applied throughout Europe. The initial stage of this Action is to gather information, primarily from within Europe, to help establish the requirements for the main components of the new pavement design method. Part of this information gathering process will be concerned with establishing the current pavement design methodology used within Europe and elsewhere. Collecting information in a standardised form by using questionnaires provided the most convenient means of assembling this large body of knowledge. The objectives of this study are:- (1) to establish current design practice; (2) to obtain a consensus on design criteria, deterioration mechanisms and design methodology; (3) to help establish requirements for a new design method; (4) to provide background information, and (5) to make recommendations for the development of a new European method of pavement design. This report collates and summarises this information with the intention of establishing the current situation, this study is not a critical review. The questionnaire was concerned only with the design method for the primary road network. Separate questionnaires were compiled for flexible and composite pavements. A flexible pavement is defined as a pavement which has asphalt surfacing and the main structural layer (base course) is either asphalt or untreated granular material while a composite pavement has a hydraulically bound base course and asphalt surfacing. This report is divided into two parts: part 1 deals with the analysis of the questionnaires for flexible pavement design and Part 2 deals with composite pavement design. Each part begins with a brief summary of the design method used by the countries or organisations that contributed information and then various aspects of design, such as climate, traffic, design inputs for each layer, and models are considered together with observed modes of pavement deterioration; finally, design examples using the various design methods are given. (A)