Improving the productivity and mobility of the national highway transportation system are key goals of the Federal Highway Administration (FHWA). During 2005, FHWA’s Long-Term Pavement Performance (LTPP) program continued to work toward these goals through its efforts to provide answers to “how” and “why” pavements perform as they do. To better understand pavement performance, the LTPP program gathers and processes data describing the structure, service conditions, and performance of more than 2,400 pavement test sections in North America. Highway engineers can use these data and findings from the analyses conducted to date to help them make decisions leading to more cost-effective and better performing pavements