Introduction

The United States reaps a substantial return from investing approximately $40 billion a year in its pavements. As large as that figure seems, a recent article in Roads & Bridges puts the annual savings from the interstate system at $737 billion when considering “safety benefits, saved time, reduced fuel, and lower consumer costs.”(1) The LTPP program, the most comprehensive pavement research program ever undertaken, addresses the issue of how to optimize this recurring investment.

The need for the LTPP program was first identified in the Transportation Research Board’s (TRB) America’s Highways: Accelerating the Search for Innovation.(2) This report, prepared by a panel of senior leaders in the transportation community, noted that highway pavements do not always live up to design expectations and recommended a “long-term field test that systematically covered a wide range of climate, soil, construction, maintenance, and loading conditions….”(2) In 1986, based on this recommendation, the American Association of State Highway and Transportation Officials (AASHTO) developed the plan for such a program to be included in the 5-year Strategic Highway Research Program (SHRP). The mission of the program, known now as the LTPP program, was to promote increased pavement life through the following:

• Collecting and storing performance data from a large number of in-service highways in the United States and Canada over an extended period to support analysis and product development.
• Analyzing these data to describe how pavements perform and to explain why they perform as they do.
• Translating these insights into knowledge and usable engineering products related to pavement design, construction, rehabilitation, maintenance, preservation, and management.

Congress funded SHRP which was managed by the National Academy of Sciences as part of Federal-aid highway authorizing legislation in 1987. LTPP field data collection began in 1989. It was always understood that the achievement of the program's objectives required that the program be continued over the long term. Therefore, as SHRP began to diminish, continuation of LTPP under the FHWA was formally authorized by Congress in the Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991. In 1992, the FHWA assumed management and administrative responsibilities to continue LTPP and complete the planned pavement performance monitoring. Monitoring has continues to further enhance the data available. New experiments are being added to address the evolution of pavement design and construction practices.