The intention of various design procedures is to provide a means to arrive at a suitable structural configuration of pavement to last the expected traffic loading. Many factors--pavement structure, soil properties, climatic effects, required condition of pavements, and traffic--are inputs in pavement design as the best estimates. There is an inherent variability in these factors, which affects the reliability of the design. The variation in traffic load under constant volume is evaluated as a factor in the design process, specifically the procedure suggested in the AASHTO Design Guide. When the AASHTO Design Guide procedure is used, the traffic loading parameter is varied over a range while other factors are maintained as constants. The variation in reliability for a given slab thickness or structural number is determined for various levels of traffic load inputs in the form of different vehicle mixes, and the trends are documented. This study establishes the variation in reliability with traffic loads that can serve as a guide regarding the accuracy of traffic load input, not only for pavement design but also for traffic data collection activities. The use of reliability curves for the estimation of service lives and remaining lives of pavements is illustrated.
Abstract