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Further Reading

In recent years much has been written on the concept of induced travel. This section offers a brief listing of further readings that discuss it in greater detail.

Background

Litman (2004) describes induced travel and its role in transportation planning. Lee (2002) provides a discussion of the relationship between elasticities and induced demand. Lee differentiates between short run elasticity (movement along the short run demand curve) and long run elasticity (movement along the long run demand curve, or a shift in the short run demand curve). Appendix A, "Induced Traffic and Induced Demand" (Lee, et al., 2002) and Appendix B, "Demand Elasticities for Highway Travel" (Lee, 2002) in the HERS-ST v2.0 Technical Report provides additional background on induced demand and the reasoning behind the elasticity values chosen for the HERS model. Chapter 4 of Transportation Research Board (1995) provides a thorough discussion of travel demand, including induced travel.

Empirical Evidence

Goodwin (1996), Noland & Lem (2002), and Cervero (2002) provide reviews of many empirical studies on induced demand. Each paper gives detailed discussion of the different types of induced demand studies and their findings. Cervero (2003) discusses potential methodological problems with past induced demand studies and offers methods that attempt to overcome these problems.

Incorporating Induced Demand in a Benefit-Cost Analysis

Appendix C, "Basic Theory of Highway Project Evaluation" (Lee, 2002) in the HERS-ST v2.0 Technical Report explains how demand functions are incorporated into a project evaluation. Lee uses short-run and long-run elasticities to estimate the benefits of transportation projects. DeCorla-Souza & Cohen (1999) demonstrate how to estimate induced demand in the case of highway expansion. The authors include the estimation of user benefits in their FHWA White Paper, "Accounting for Induced Travel in Evaluation of Urban Highway Expansion" (DeCorla-Souza & Cohen, no date). Abelson & Hensher (2001) explain how to evaluate the user benefits of induced travel. In Litman (2004), a discussion is given on how to incorporate induced demand in travel forecasts and how to evaluate the effects of induced demand.

Sources

P.W. Abelson and D. A. Hensher (2001), "Induced Travel and User Benefits: Clarifying Definitions and Measurement for Urban Road Infrastructure." In Handbook of Transport Systems and Traffic Control, edited by Kenneth J. Button and David A. Hensher. Pergamon.

Robert Cervero (2002), "Induced Travel Demand: Research Design, Empirical Evidence, and Normative Policies." In Journal of Planning Literature, Vol. 17, No. 1. August.

Robert Cervero (2003), "Are Induced-Travel Studies Inducing Bad Investments?" Access, No. 22, Spring 2003, pp. 22-27.

Patrick DeCorla-Souza and H. Cohen. "Accounting for Induced Travel in Evaluation of Urban Highway Expansion." Surface Transportation Efficiency Analysis Model (STEAM), Federal Highway Administration. No Date. Available at: http://www.fhwa.dot.gov/steam/doc.htm.

Federal Highway Administration (2002), HERS-ST v20: Highway Economic Requirements System - State Version Technical Report. FHWA-IF-02-060. Federal Highway Administration, Office of Asset Management. Washington DC. Available at: http://www.fhwa.dot.gov/infrastructure/asstmgmt/hersdoc.htm

Philip B. Goodwin (1996), "Empirical Evidence on Induced Traffic: A Review and Synthesis". Transportation 23,  pp. 35-54.

D.B. Lee, L. A. Klein, and G. Camus (2002), "Appendix A: Induced Traffic and Induced Demand." In HERS-ST v20: Highway Economic Requirements System - State Version Technical Report. FHWA-IF-02-060. Federal Highway Administration, Office of Asset Management. Washington DC. Available at: http://www.fhwa.dot.gov/infrastructure/asstmgmt/hersdoc.htm. Accessed March 2004.

D.B. Lee (2002), "Appendix B: Demand Elasticities for Highway Travel." In HERS-ST v20: Highway Economic Requirements System - State Version Technical Report. FHWA-IF-02-060. Federal Highway Administration, Office of Asset Management. Washington DC. Available at: http://www.fhwa.dot.gov/infrastructure/asstmgmt/hersdoc.htm. Accessed March 2004.

D.B. Lee (2002), "Appendix C: Basic Theory of Highway Project Evaluation." In HERS-ST v20: Highway Economic Requirements System - State Version Technical Report. FHWA-IF-02-060. Federal Highway Administration, Office of Asset Management. Washington DC. Available at: http://www.fhwa.dot.gov/infrastructure/asstmgmt/hersdoc.htm. Accessed March 2004.

D.B. Lee (2002), HERS-ST v20: Highway Economic Requirements System - State Version: Induced Demand and Elasticity. FHWA-IF-02-055. Federal Highway Administration, Office of Asset Management. Washington DC. August 2002. Available at: http://www.fhwa.dot.gov/infrastructure/asstmgmt/hersdoc.htm. Accessed March 2004.

Todd Litman (2001), “Generated Traffic: Implications for Transport Planning,” ITE Journal, Vol. 71, No. 4, Institute of Transportation Engineers (www.ite.org), April, pp. 38-47. Available at: http://www.vtpi.org/gentraf.pdf.

Robert B. Noland and L. L. Lem (2002). "A Review of the Evidence for Induced Travel and Changes in Transportation and Environmental Policy in the US and the UK." Transportation Research Part D 7, pp. 1-26.

SACTRA (1994), Trunk Roads and the Generation of Traffic, Standing Advisory Committee on Trunk Road Assessment, UKDoT, HMSO (London; www.roads.detr.gov.uk/roadnetwork).

Transportation Research Board (1995), Expanding Metropolitan Highways: Implications for Air Quality and Energy Use. TRB Special Report 245. Washington D.C.

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