The National Academies

NCHRP 20-24(54)G [Completed]

2006 AASHTO Bottom Line Scoping
[ NCHRP 20-24 (Administration of Highway and Transportation Agencies) ]

  Project Data
Funds: $300,000
Research Agency: Cambridge Systematics, Inc.
Principal Investigator: Arlee Reno, Alan Pisarski
Effective Date: 11/7/2007
Completion Date: 5/6/2009

For the past several years, the Federal Highway Administration (FHWA) has used the Highway Economic Requirements System (HERS) and National Bridge Investment Analysis System (NBIAS) software models to estimate future investment requirements for roadways and bridges of the Nation's highway system. The U. S. Department of Transportation (USDOT) reports these estimates to the Congress in the agency’s biennial Conditions and Performance Report. (C&P)
The models have introduced well-structured benefit-cost analysis methods into the national investment-needs assessment process, estimating the total costs of highway and bridge improvements that are warranted by user-cost savings and other benefits likely to accrue if these investments are made. The models are sophisticated and complex, but represent a reasoned and defensible approach to projecting the investment required to maintain and improve the highway system to serve the nation’s economy. To make this approach accessible to the state agencies that are responsible for managing the system, FHWA has produced the Highway Economic Requirements System - State Version (HERS-ST), an extension of the HERS model that individual states can use to predict the investment required to maintain defined highway system performance levels on the state’s highway system.
Despite the improvements brought to national and state-level investment needs analyses by the HERS, NBIAS, and HERS-ST models, there are still uncertainties associated with the investment-needs projections. For example, the models rely on assumptions reflecting model-users’ expectations about future economic conditions, travel demand, and other parameters influencing the models’ outcome. Estimated investment requirements may vary as these assumptions are changed to reflect the particular expectations and perspectives of different users.  In addition, there are potentially substantial investments--for example, in highway interchanges or maintenance of traffic flow during major reconstructions – that may be neglected or very indirectly estimated by the models but needed to ensure system performance. These investment needs must be estimated using other methods.
In 2002, the American Association of State Highway and Transportation Officials (AASHTO) prepared a Highway and Transit Bottom Line report based on independent analysis of national highway and public transportation investment needs.  This analysis employed models used by FHWA and incorporated data and results of the model used by the Federal Transit Administration (FTA), but reflected the perspectives of the states. AASHTO’s goals in preparing that report were to ensure that national resource needs are appropriately assessed and that state perspectives on investment needs are effectively identified and represented in legislative and other policy discussions. The analysis provided a basis for engaging state and federal policy makers in discussions of significant issues shaping the legislative agenda.  Such discussions must continue as policy makers consider future transportation legislation.
The objective of this project was to emulate and improve upon  the process used to develop the AASHTO 2002 Bottom Line report as it applied to highways, with updated and enhanced analyses, to produce information on investment needs for preparation of a 2009 report. The project was conducted in two parts: (A) application of HERS, NBIAS, and HERS-ST models and other analysis procedures with parameters reflecting the states’ priorities and best available information to produce investment needs estimates, and (B) assessment of the implications of these investment needs estimates and assistance to AASHTO staff in preparation of AASHTO's 2009 Bottom Line Report.  A consultant's final report was delivered to AASHTO. 

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