Modeling Mechanistic-Empirical Road Design: The Case for Kenyan Roads

Abstract

Regular revision of road design manuals is a recommended practice in pavement management, and Kenya has recently completed a review of hers. The outcome of the process is an enhanced but empirical manual with rigid models. The reviewers (BCEOM egis, a geotechnical consul tancy) however strongly recommended the use of interactive mathemati cal models of a mechanistic-empirical (ME) nature in road design for the country in future, since ME models more accurately predict pavement performance than the rigid ones currently in empirical manuals. Using ME models in road design in Kenya now is a challenge since the climatic models in ME design require inputs of hourly intervals, yet most weather stations keep only daily interval records. This study investigated the pos sibility of adapting the existing ME mathematical models for use in road design in Kenya. We achieved this by rigorously analyzing the differ ential equations and other equations contained in the ME mathematical models. Simulating hourly weather data from daily data was applied for some weather elements, while adaptation of the governing equations in the models to take inputs of daily intervals was done for the others. Secondary climatic data obtained from the Kenya Meteorological Depart ment and theWeatherbase websites were used as inputs into the models. The study established that with suitable adaptation, the existing climatic data can be used as inputs into the models with little loss in the relia bility of their predictions, hence Kenya can successfully embrace the ME pavement approach. The findings of this study could serve as an initial step towards the realization of the reviewers' recommendations on use of ME mathematical models over empirical manuals.