Engineering Application of Washington State’s Pavement Management System

Abstract

Previous investigation into the Washington State Department of Transportation’s (WSDOT) Pavement Management System (WSPMS) revealed pavement sections on the state route system that were outperforming or underperforming other pavement sections constructed of similar materials and subjected to similar traffic and environmental conditions. Reasons were not clear. The WSPMS was used to identify superior and inferior candidate pavements for further investigation. All state route pavements were stratified into 18 distinct analysis groups, and population statistics were generated for each group providing WSDOT with a snapshot of the current “state of the state route system” and providing the basis for selecting candidate pavements. The five performance measures considered included: age of the surface course, a distress-based pavement structural condition score, annual design-lane equivalent single axle loads, roughness (in terms of International Roughness Index), and rutting. Results of the analysis suggest that WSDOT is properly designing layer thicknesses at appropriate reliability levels. Also, in 6 of 10 analysis group comparisons, inferior pavements were actually thicker than superior pavements. Both findings suggest that thickness design factors are not the primary cause of inferior performance in Washington State; construction, material and site specific factors are likely the cause. Additionally, in an international effort to exchange information on pavement performance and construction practices, highlights of a comparative study of pavement performance with South Africa’s Gauteng Department of Transportation are presented.