One of the most common economic evaluation methods is Benefit-Cost (also called Cost-Benefit) analysis, which uses monetized (measured in monetary units) values to compare total incremental benefits with total incremental costs. The results can be presented as a ratio, with benefits divided by costs (which is why it is often called Benefit/Cost or B/C analysis). Net Benefits is defined as the sum of all benefits minus the sum of all costs, which provides an absolute measure of benefits (total dollars), rather than the relative measures provided by B/C Ratio.
To perform Benefit-Cost Analysis it is necessary to monetize all relevant impacts. In recent years economists have developed techniques for monetizing non-market impacts, and some transportation agencies have adopted standardized values for travel time, crash damages and environmental impacts.
Benefit-Cost Analysis is most applicable for evaluating proposed projects that meet the following criteria:
(1) The potential project expenditure is significant enough to justify spending resources on forecasting, measuring and evaluating the expected benefits and impacts.
(2) The project motivation is to improve the transportation system's efficiency at serving travel and access-related needs, rather than to meet some legal requirement or social goal.
(3) Environmental or social impacts that are outside of the transportation system efficiency measurement are either: (a) negligible in magnitude, (b) measurable in ways that can be used within the benefit-cost framework, or (c) to be considered by some other form of project appraisal outside of the benefit-cost analysis.
During the last few decades Benefit-Cost analysis has been widely used to evaluate transportation projects, and standardized methods have been developed, including software programs such as MicroBenCost and HDM-4 (CalTrans 2006; World Bank 2011). These are generally designed to evaluate a particular type of transport improvement, such as highways or transit service, and are generally inappropriate for comparing the net benefits of improvements to different modes or of transportation demand management strategies such as pricing reforms or commute trip reduction programs because they do not account for many significant impacts. For example, conventional benefit-cost models generally ignore parking facility costs, and therefore the parking cost savings that result when travelers shift from driving to alternative modes. Most models only account for changes in vehicle operating costs, but ignore vehicle ownership costs, and therefore the savings to consumers from improvements in alternative modes that allow households to reduce their vehicle ownership. Most include no factor for the social equity benefits that result from improving basic mobility for non-drivers, for example, from projects that improve affordable modes such as walking, cycling and public transport. It is therefore important that people who use these models and model results understand their limitations and biases.
Benefit-Cost Analysis is neither necessary nor desirable to justify all transportation projects. It may not always be appropriate in the following cases:
- Projects motivated by a need to meet legal requirements — such as safety standards, handicapped access standards or environmental impact standards. Changes in population growth, urban development, travel patterns or legal regulations may necessitate new projects to upgrade existing transportation facilities and services, build new facilities or provide new services to meet those current legally required standards.
- Projects motivated primarily by a need to address distributional equity concerns — i.e., legal, political or moral desires for fairness. This includes the provision of some minimum level of basic (road, transit, air or sea) access for isolated or ill-served regions, communities or neighborhoods. It can also include some projects motivated by economic development, i.e., enabling the attraction and creation of new jobs particularly in economically depressed areas. Finally, some decisions are based on the desire (and in some cases, the legal need) to avoid selection of projects and project designs that focus undue negative impact on socially vulnerable groups (such as low income, elderly, or minority groups)
- Projects that are merely maintaining, renovating or rehabilitating already-built transportation facilities, which are necessary to avoid losing the already-demonstrated benefits of those existing facilities (unless there are viable alternatives present)
It is also inappropriate to rely solely on Benefit-Cost Analysis in situations where there are special concerns that must also be considered outside of that analysis. Since benefit-cost analysis focuses on the comparison of total benefits and total costs in dollar terms, some particular concerns affecting a given project may be either hidden or missed within the calculation of total benefits and total costs. In some cases, the desirability of projects needs to be considered in terms of their effectiveness at reducing certain key objectives — such as air pollution reduction, creation of new jobs, or improving mobility for physically, economically and socially disadvantaged people. In such cases, cost-effectiveness analysis (which measures environmental or social benefits per dollar of transportation project spending) may be appropriate, either in addition to or instead of benefit-cost analysis.
CalTrans (2006), Benefit-Cost Models, Office of Transportation Economics, California Department of Transportation (www.dot.ca.gov/hq/tpp/offices/ote). Available at: www.dot.ca.gov/hq/tpp/offices/ote/benefit_cost/index.html.
CTE (Center for Transportation and the Environment) (2008), Improved Methods For Assessing Social, Cultural, And Economic Effects Of Transportation Projects, NCHRP Project 08-36, Task 66, TRB (www.trb.org) and the American Association of State Highway and Transportation Officials (AASHTO). Available at: www.statewideplanning.org/_resources/234_NCHRP-8-36-66.pdf.
CUTR (2007), Economics of Travel Demand Management: Comparative Cost Effectiveness and Public Investment, Center for Urban Transportation Research (www.nctr.usf.edu). Available at: www.nctr.usf.edu/pdf/77704.pdf
DFID (2001), New Economists Guide: Appraisal Of Investments In Improved Rural Access, UK Department for International Development (www.transport-links.org). Available at: www.transport-links.org/Economist%20Guide/English/Intro.htm.
DFID (2003), Social Benefits in Transport Planning, UK Department for International Development (www.transport-links.org). Available at: www.transport-links.org/transport_links/projects/projects_document_page.asp?projectid=322).
Mark Delucchi (2005), The Social-Cost Calculator (SCC): Documentation of Methods and Data, and Case Study of Sacramento, Sacramento Area Council of Governments and the Northeast States for Coordinated Air-Use Management, UCD-ITS-RR-05-37, (www.its.ucdavis.edu).
DfT (2006), Transport Analysis Guidance, Integrated Transport Economics and Appraisal, UK Department for Transport (www.webtag.org.uk/index.htm).
EDRG (2007), Monetary Valuation of Hard-to-Quantify Transportation Impacts: Valuing Environmental, Health/Safety & Economic Development Impacts, NCHRP 8-36-61, National Cooperative Highway Research Program (www.trb.org/nchrp). Available at: www.statewideplanning.org/_resources/63_NCHRP8-36-61.pdf.
EEB (1994), Guide to Benefit-Cost Analysis in Transport Canada, Economic Evaluation Branch, Transport Canada (www.tc.gc.ca); at www.tc.gc.ca/eng/corporate-services/finance-bca-114.htm.
European Transport Pricing Initiatives (www.transport-pricing.net) includes various research on fair and efficient pricing.
FHWA (2005), Highway Economic Requirements System (HERS): Technical Report, Federal Highway Administration (www.fhwa.dot.gov); at www.fhwa.dot.gov/asset/hersst/pubs/tech/tech00.cfm.
Todd Litman (2001), What’s It Worth? Life Cycle and Benefit/Cost Analysis for Evaluating Economic Value, Presented at Internet Symposium on Benefit-Cost Analysis, Transportation Association of Canada (www.tac-atc.ca). Available at: www.vtpi.org/worth.pdf.
Todd Litman (2008), Well Measured: Developing Indicators for Comprehensive and Sustainable Transport Planning, VTPI (www.vtpi.org); at www.vtpi.org/wellmeas.pdf. Summary published as “Developing Indicators For Comprehensive And Sustainable Transport Planning,” Transportation Research Record 2017, Transportation Research Board (www.trb.org), 2007, pp. 10-15; at www.vtpi.org/sus_tran_ind.pdf.
Louis Berger Inc (1998), Guidance for Estimating the Indirect Effects of Proposed Transportation Projects, NCHRP Report 403, Transportation Research Board (www.trb.org). Also see Louis Berger Group (2001), Guidance for Assessing Indirect and Cumulative Impacts of Transportation Projects in North Carolina, North Carolina Department of Transportation (www.ncdot.org/~research).
M. Maibach, et al. (2008), Handbook on Estimation of External Cost in the Transport Sector, CE Delft (www.ce.nl). Available at: http://ec.europa.eu/transport/costs/handbook/doc/2008_01_15_handbook_external_cost_en.pdf
Marsden Jacob Associates (2005), Frameworks For Economic Impact Analysis And Benefit-Cost Analysis, Economic Regulation Authority, Western Australia (www.era.wa.gov.au). Available at: www.era.wa.gov.au/water/library/Frameworks_for_economic_analysis_and_benefit_cost_analysis.pdf.
NZTA (2010), Economic Evaluation Manual (EEM), New Zealand Transport Agency (www.nzta.govt.nz); at www.nzta.govt.nz/resources/results.html?catid=401.FHWA, Toolbox for Regional Policy Analysis Website (www.fhwa.dot.gov/planning/toolbox/index.htm) describes analytical methods for evaluating regional economic, social and environmental impacts of transportation and land use policies.
Nariida C. Smith, Daniel W. Veryard and Russell P. Kilvington (2009), Relative Costs And Benefits Of Modal Transport Solutions, Research Report 393, NZ Transport Agency (www.nzta.govt.nz). Available at: www.nzta.govt.nz/resources/research/reports/393/docs/393.pdf.
TC (2003-2007), The Full Cost Investigation of Transportation in Canada (multiple documents), Transport Canada (www.tc.gc.ca); at www.tc.gc.ca/pol/en/aca/fci/menu.htm. Technical report, Anming Zhang, Anthony E. Boardman, David Gillen and W.G. Waters II (2005), Towards Estimating the Social and Environmental Costs of Transportation in Canada, Centre for Transportation Studies, UBC, for Transport Canada (www.sauder.ubc.ca/cts). Available at: www.sauder.ubc.ca/cts/docs/Full-TC-report-Updated-November05.pdf.
Transport Analysis Guidance Website (www.webtag.org.uk) by the UK Department for Transport, provides advice on transport modeling and economic evaluation.
van Essen, et al (2004), Marginal Costs of Infrastructure Use – Towards a Simplified Approach, CE Delft (www.ce.nl). Available at: www.ce.nl/?go=home.downloadPub&id=456&file=04_4597_15.pdf.
World Bank (2008), A Framework For Urban Transport Projects: Operational Guidance for World Bank Staff, Transport Sector Board, World Bank (www.worldbank.org). Available at: http://siteresources.worldbank.org/INTTRANSPORT/Resources/tp_15_urban.pdf.