Highway Infrastructure: FHWA's Model for Estimating Highway Needs Is Generally Reasonable, Despite Limitations
RCED-00-133
Published: Jun 05, 2000. Publicly Released: Jun 05, 2000.
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Highlights
Pursuant to a legislative requirement, GAO provided information on how the Federal Highway Administration (FHwA) determines highway investment requirements, focusing on the: (1) methodology the Highway Economic Requirements System (HERS) computer model uses to generate its estimates of the nation's highway investment requirements; (2) strengths and limitations of the model; and (3) usefulness of the HERS estimates for deciding on federal investments in highway infrastructure.
Recommendations
Recommendations for Executive Action
| Agency Affected | Recommendation | Status |
|---|---|---|
| Department of Transportation | In order to ensure that the HERS model achieves its objectives and that the limits of its estimates and the estimates presented in future conditions and performance reports are disclosed, the Secretary of Transportation should direct the Administrator, FHwA, to establish a timeframe for revising the HERS model in order to account for the expected lifetime benefits that are associated with alternative highway improvement options. |
Closed – Implemented
DOT concurs with this recommendation. FHWA began work in fiscal year 2000, to eliminate the computational shortcut currently used to approximate the future lifetime benefits of an improvement. The Department established a timeframe--September 2001--for completion of work minimizing the effect of the computational shortcut. The contractor will consider using a single, long time period for all benefit cost analyses in the model and making the necessary changes to the model.
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| Department of Transportation | In order to ensure that the HERS model achieves its objectives and that the limits of its estimates and the estimates presented in future conditions and performance reports are disclosed, the Secretary of Transportation should direct the Administrator, FHwA, to clarify, when presenting the HERS estimates, that there are uncertainties associated with the estimates and refer readers to the sensitivity analyses performed on the HERS model that illustrate these uncertainties. |
Closed – Implemented
DOT concurred with this recommendation. The Department of Transportation's January 2003 report on investment requirements, introduced the estimates of investment requirements and their associated sensitivity analyses together, helping a reader to find critical needs forecases and clear information about the uncertainties associated with them.
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| Department of Transportation | In order to ensure that the HERS model achieves its objectives and that the limits of its estimates and the estimates presented in future conditions and performance reports are disclosed, the Secretary of Transportation should direct the Administrator, FHwA, to explain in the report that one portion of the estimate for highway investment requirements is from the HERS model and is based on benefit-cost analyses and that the other portion was calculated using less reliable methods, as well as the percentage that each of these portions constitutes of the overall estimate. |
Closed – Implemented
DOT concurred with this recommendation. In its January 2003 report on highway investment requirements, DOT included an exhibit that identified the source and amount of each component that contributed to the overall estimate of future highway and bridge investment requirements. This alerted readers to the relative rigor of the different components of the estimate.
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Topics
Computer modelingCost effectiveness analysisData integrityFederal aid for highwaysHighway engineeringHighway planningHighway researchLife cycle costsManagement information systemsPavement performancePublic roads or highwaysRoad surfacesTraffic lanes