In the present study, an effort has been made to analyse the data of certain overlaid flexible pavements to assess the performance variation of different influencing parameters with time. The influencing parameters considered in this study are deflection (predicting the structural condition), rutting and cracking (predicting the functional condition) and the availability of resources for the choice of the type and thickness of materials for overlays (predicting the maintenance cost). The data have been analysed for pre-monsoon, post-monsoon and winter season for the years between 1980 to 1992. The overlays on the test sections with different types and thickness of materials were laid during 1985-1986 based on the analysis of data collected during 1980-1985. The performance and life of overlays have been assessed on the basis of acceptable limits for deflection, rut depth, cracks and cracking pattern and maintenance cost. A general model is developed considering the data of all the test sections which predict life of overlays of different materials and thicknesses. The various parameters considered in the development of the models are characteristic deflection, rut depth, crack length, pavement thickness, overlay thickness and traffic volume. Since the properties of the subgrade soil affect the performance of pavements considerably, the models are also developed for each type of subgrade encountered in the flexible pavements under study. The models developed herein are found to be capable for predicting life of an overlay with a fair degree of accuracy. The maintenance decisions can be taken, keeping in view the influence of any one or more of the parameters which reach their maximum acceptable limits first. The choice of materials for an overlay can be made on the basis of economic considerations without sacrificing the safety of the road structure. (A)
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