Transportation Infrastructure

A road test conducted by the American Association of State Highway Officials in 1959-60 found that heavy trucks cause more highway pavement damage than do other vehicles. On the basis of this test, the Association developed an initial pavement design guide in 1961, which has been updated periodically since then. The Federal Highway Administration (FHWA) has neither adopted the guide nor mandated its use by states. Rather, FHWA requires that sound engineering and management principles and practices be used in pavement design. This report (1) describes the roles of FHWA and others in developing and updating the pavement design guide and (2) examines the use and the potential of a computer analysis method known as the nonlinear 3 dimensional-finite element method for improving the design and the analysis of highway pavement structures.

GAO noted that: (1) FHwA has worked cooperatively with the American Association of State Highway and Transportation Officials (AASHTO) in developing and updating the pavement design guide; (2) the current guide is slated to be updated by the year 2002 to better reflect the changing priority of rehabilitating the nation's highways rather than building new ones; (3) in contrast to the current guide, that many transportation experts believe is outdated, the new guide is expected to incorporate the use of analytical methods to predict pavement performance under various loading and climatic conditions; (4) sponsors believe that a new design approach will more realistically characterize existing highway pavements and improve the reliability of designs; (5) a promising analytical method to accurately predict pavement response is the nonlinear 3D-FEM; (6) only with accurate response data can one reliably predict pavement performance; (7) the use of this method has the potential to improve the design of highway pavements, which encompasses highway safety, durability, and cost-effectiveness, because values of stresses, strains, and deflections (pavement response) can be calculated accurately from a variety of static, impact, vibratory, and moving mixes in traffic loads; (8) several state departments of transportation, academicians, and scientists have pioneered the use of the nonlinear 3D-FEM and are using it to solve a variety of complex structural engineering problems, including the design and analysis of highway pavement structures; and (9) while this is a promising method for improving highway pavement design and analysis, GAO could find no evidence that it is being considered for inclusion in the current design guide update.

Recommendations

Our recommendations from this work are listed below with a Contact for more information. Status will change from "In process" to "Open," "Closed - implemented," or "Closed - not implemented" based on our follow up work.

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