Guidebook for Assessing the Social and Economic Effects of Transportation Projects

David J. Forkenbrock
Glen E. Weisbrod
2001

Traditionally, potential transportation projects have been evaluated on the basis of a combination of engineering and economic criteria. For a project to be selected, it must improve such important performance measures as total travel time through a network and safety. In recent years, however, increased attention is being given to the effects of transportation projects on members of society other than users of the facility to be improved.

Because assessments of the likely social and economic effects of transportation projects have received only limited attention, a need exists to increase the capabilities of transportation professionals to predict and assess these effects. This guidebook defines 11 general types of social and economic effects and provides insights into the suitability of the methods, tools, and techniques available to assess them.

Applying the best possible methods of analysis is important because a comprehensive assessment of social and economic effects of a proposed transportation project is inherently complex. Among the reasons why assessing these effects is complex is that:
• A balance has to be drawn between benefits to users of the facility and effects on other community residents.
• Even among community residents, numerous effects interact and must be traded off, some are positive, others negative.
• Various population groups within the community may be affected quite differently in terms of mixes of effects.

Methods for assessing various types of social and economics effects vary as much as the effects themselves. Some effects, like changes in user costs, normally lend themselves to extensive quantification. The issue in the case of these effects often is the values to assign to key parameters, such as the value of travel time or the values of lives saved and injuries prevented by a safety enhancement. Other effects tend to be far more abstruse. Effects such as the change in visual quality or community cohesion are bound to be rather subjective in nature. What is a positive effect to one person may not be so to another, and it is difficult to assign a numerical value to these effects. In fact, many social and economic effects are qualitative in nature and must be treated as such in impact analyses.

Ultimately, then, the purpose of this guidebook is to improve the capacity of transportation professionals to take into account a wide array of social and economic effects when evaluating possible projects. Emphasis is placed on the methods, tools, and techniques most likely to produce analyses that can be understood by community residents and decision-makers.

242 pp. 19 figures, 38 tables, glossary

NOTE: This document is not distributed by the Public Policy Center. It is available as National Cooperative Research Program (NCHRP) Report 456 for $63.00 from the Transportation Research Board, National Research Council, 2101 Constitution Avenue, N.W., Washington, D.C. 20418. It also can be ordered through the Internet at: http://www.national-academies.org/trb/bookstore