United States Government Publishing Office publisher pbl distributor dst United States Government Accountability Office Resources, Community, and Economic Development Division author aut Government Organization text government publication eng GAOREPORTS Legislative Agency Publications gao legislative 2010-08-12 U.S. Government Printing Office 2000-06-05 monographic deposited born digital 43 p. GA 1.13:RCED-00-133 https://www.govinfo.gov/app/details/GAOREPORTS-RCED-00-133 P0b002ee180392381 f:rc00133 DGPO 2010-08-12 2011-03-24 GAOREPORTS-RCED-00-133 machine generated eng fdlp REPORT GAOREPORTS-RCED-00-133 RCED-00-133 Highway research Highway planning Data integrity Public roads or highways Management information systems Cost effectiveness analysis Computer modeling Life cycle costs Highway engineering Federal aid for highways DOT Highway Economic Requirements System Letter Report RCED

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.<p/>GAO noted that: (1) the HERS computer model estimates investment requirements for the nation's highways by adding together the costs of highway improvements that the model's benefit-cost analyses indicate are warranted; (2) in making its estimates, the model relies on extensive data on highway segments throughout the nation, such as pavement conditions and expected growth in traffic; (3) the model also uses information, such as vehicle operating costs and emissions' obtained from other sources; (4) the HERS model uses the data to: (a) project the future condition and performance of the highway system; (b) assess whether any highway improvements are warranted; and (c) select and implement appropriate improvements; (5) such improvements range from resurfacing a highway to adding lanes and are based on a comparison of the construction costs and the lifetime benefits of the improvement; (6) a major strength of the model is its ability to assess the relative benefits and costs associated with alternative options; (7) the model has limitations, however, in that it: (a) does not completely account for the effect of highway improvements on all other highways and modes of transportation; (b) does not fully account for the uncertainties associated with its methods, data, and assumptions; (c) relies on a computational shortcut to approximate the future lifetime benefits of an improvement; and (d) uses data that vary in quality; (8) HERS estimates can be useful as a general guide for the investment requirements of the nation's highways included in the model, and for assessing relative investment requirements over time; (9) nevertheless, limitations and uncertainties associated with making forecasts prevent the estimates from being a precise forecast of highway investment requirements; (10) FHwA includes the HERS estimates in its current report on the conditions and performance of the nation's highways, bridges, and transit systems; (11) in the report, however, FHwA does not clearly disclose the level of uncertainties in the HERS estimates; (12) furthermore, to derive a total estimate of highway investment requirements, FHwA combines the HERS estimates with estimates for other types of highways and investments that are not based on benefit-cost analyses; and (13) as a result, the report's readers are not likely to be aware of the imprecision of the HERS estimates and the fact that only part of the total highway investment requirements is estimated on the basis of an assessment of the benefits and costs of alternative improvement options. https://www.govinfo.gov/content/pkg/GAOREPORTS-RCED-00-133/html/GAOREPORTS-RCED-00-133.htm https://www.govinfo.gov/content/pkg/GAOREPORTS-RCED-00-133/pdf/GAOREPORTS-RCED-00-133.pdf GAO/RCED-00-133 https://www.govinfo.gov/app/details/GAOREPORTS-RCED-00-133 Letter Report GAO/RCED-00-133; Highway Infrastructure: FHWA's Model for Estimating; Highway research Highway planning Data integrity Public roads or highways Management information systems Cost effectiveness analysis Computer modeling Life cycle costs Highway engineering Federal aid for highways DOT Highway Economic Requirements System Title 23 Section 502(g) 23 U.S.C. 502(g) Title 49 Section 308(e) 49 U.S.C. 308(e) Public Law 105-178