Effect of Traffic Data Coverage on the M-E PDG Traffic Characterization

Abstract

The Mechanistic-Empirical Pavement Design Guide (M-E PDG) requires detailed traffic data to characterize the axle loads and their repetitions, and subsequently predict pavement performance. For level 1, the M-E PDG requires, at 95% confidence level, 84 days of coverage for traffic data i.e., one week per month (OWPM). The data coverage can produce 1 to 2% errors in axle load and truck traffic distributions, as well as 5 to 10% error in annual average daily travel time (AADTT) values. In preliminary analyses of five WIM sites in Michigan, it was found that OWPM data produced significant variation in monthly distribution factors and AADTT, especially for sites with AADTT less than 1000 vehicles. Subsequent M-E PDG analyses using OWPM versus continuous traffic data yielded significant variation in predicted pavement performance. Therefore, the objective of this paper is to investigate whether using OWPM WIM data is equivalent to continuous WIM data when determining traffic characteristics—truck traffic classification (TTC), axle load distribution, monthly distribution factors (MDFs), hourly distribution factors (HDFs), axle groups per vehicle (AGPV) and AADTT. To accomplish the study objective, traffic characterizations from one week and continuous data coverage from 34 weigh in motion (WIM) sites in Michigan were obtained and compared in order to provide confidence intervals in terms of traffic characterization and pavement performance differences between OWPM and continuous data.