Environmental and traffic deterioration with mechanistic-empirical pavement design model: Canadian example

Limited budgets are resulting in a need for better design of low-volume roads. Traffic loading, environmental conditions, subgrade soil, and construction and maintenance quality are among the various factors that influence pavement performance and must be considered in the design process. Environmental conditions have a significant impact on the performance of low-volume pavements. Performance-graded asphalts, which are mixes designed for the in-service environment of the pavement, are vital in Canada, where low-temperature cracking has been a prevalent distress. In addition, southern Ontario has a moderate climate with high traffic volumes, whereas in northern Ontario the winters are severe and traffic loading is lower. A mechanisticempirical (M-E) model is described that has been developed for Ontario, the Ontario Pavement Analysis of Cost (OPAC 2000) model, and the data presented relate specifically to low-volume roads, namely, collector and local facilities. The M-E model incorporates elastic layer analysis to predict pavement response. It uses cumulative equivalent single-axle loads, subgrade type, and layer thickness to determine the most effective design. The pavement performance is based on the cumulative effect of the environment and traffic. The output of the M-E model is predicted pavement performance and projected economic impacts on the agency and the public. Examples are provided to illustrate the relative deterioration and performance curves for various design situations. For instance, the predicted total life-cycle economic impact of low-volume roads in Ontario, per kilometer, ranges from $250,000 to $750,000 (Canadian). Although this system was initially developed for Ontario conditions, the M-E model can be recalibrated to apply to other conditions.