Highway Pavement Design Guide Is Outdated
RCED-98-9: Published: Nov 21, 1997. Publicly Released: Nov 21, 1997.
- Full Report:
GAO provided information on the: (1) roles of the Federal Highway Administration (FHwA) and others in developing and updating the pavement design guide; and (2) use and potential of a computer analysis method known as nonlinear 3 Dimensional-Finite Element Method (3D-FEM) for improving the design and 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rather than building new ones; (3) in contrast to the current guide, that many transportation experts believe is outdated, the new guide is expected to incorporate the use of analytical methods to predict pavement performance under various loading and climatic conditions; (4)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.
Recommendation for Executive Action
Status: Closed - Implemented
Comments: The Department of Transportation (DOT) concurs with the recommendation. DOT is encouraging full consideration of 3D-FEM, along with other quantitative analytical methods, for pavement analysis in the updated version of the AASHTO Highway Pavement Design Guide, which is expected to be published by 2002. The recently completed phase I of this effort identified 3D-FEM as one of several available procedures to be considered also. Based on a September 2000 discussion with FHWA Program officials, FHWA is working closely with AASHTO, the organization responsible for publishing the Highway Pavement Design Guide. FHWA is also coordinating with the National Cooperative Highway Research Program (NCHRP). NCHRP is providing support for this effort. AASHTO officials and staff associated with the NCHRP effort said that they will consider nonlinear 3D-FEM in the update of the design guide. Therefore, the recommendation has been acted upon. The guide is currently in draft and will not be issued in final form until 2002.
Recommendation: To better assist in designing safer, longer lasting, and more cost-effective new, reconstructed, and overlay highway pavement structures, the Secretary of Transportation should direct the Administrator, FHwA, to ensure that the nonlinear 3D-FEM is considered in the current update of the pavement design guide.
Agency Affected: Department of Transportation