Low-Volume Road Performance Related to Traffic Loadings at Minnesota Road Research Project

Abstract

The Minnesota Department of Transportation built the Minnesota Road Research Project (MnROAD) between 1990 and 1993. The low-volume road consists of a two-lane roadway that originally contained hot-mix asphalt (HMA) and portland cement concrete (PCC) test sections. Each of these test sections is trafficked by a controlled five-axle tractor-semitrailer. The trucks have two different load configurations, resulting in the same equivalent single-axle loads (ESALs) over time. The first configuration consists of a legally loaded 80,000-lb (80-kip) truck that runs on the inside lane 4 days per week, and the second configuration consists of an overloaded 102,000-lb (102-kip) truck that runs on the outside lane 1 day per week. The field performances of the different MnROAD test sections over time resulting from the different loading applications are compared. As expected, the thermal cracking performance of HMA was not affected by the traffic loadings, because it is a distress caused by the environment. Similarly, the ride quality of both HMA and PCC pavements was not noticeably different between the two lanes. However, rutting and fatigue cracking of asphalt pavements and faulting of PCC pavements were more severe in the lane with the 80-kip truck than they were in the lane with the 102-kip truck. The higher number of repetitions at a lower load level in the 80-kip lane produced more distress than did the lower number of repetitions at a higher load level in the 102-kip lane. The data presented show that the concept of ESALs may not be appropriate for mechanistic–empirical design procedures.