Abstract
Mathematical models of transportation systems have played a prominent role in transportation planning throughout the world since the 1960s. These models are hypotheses of how people use transport systems. They provide a means of extrapolating the necessarily limited empirical evidence of how road users respond to changes in the road system. However, it needs to be recognised that these extrapolations rely for their validity on the realism of the underlying theories; transportation models can only tell us about the relationships actually built into them.
This paper reviews the limited number of studies undertaken mainly in the UK in which calibrated transportation models have been used in a systematic way to give some insight into the relative importance of the various components of induced traffic. These studies include analyses of the effects of road schemes using: a theoretical single link model; conventional four-stage transportation models of Cardiff and Belfast; elasticity models in Cardiff, Belfast, West London and Norwich; land-use interaction models in Leeds, Bilbao, Dortmund; and a model of land-use effects in Norwich. The results tell us two things: (a) the scale of the various elements of induced traffic, and (b) the implications for the economic benefits of road schemes.
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References
Bates J, Brewer M, Hanson P, McDonald D & Simmonds D (1991) Building a strategic model for Edinburgh. Proceedings of PTRC Summer Annual Meeting.
Coombe D, Leigh S & Chua H (1989) The sources of benefits from urban road improvements. Proceedings of PTRC Summer Annual Meeting.
Coombe RD, Forshew IG & Bamford TJG (1990) Assessment in the London Assessment Studies. Traffic Engineering and Control 31(10): 510–518.
Coombe D (1992) Proof of Evidence on Induced Traffic given at the Public Inquiry into Norwich Inner Ring Road Phase III.
Halcrow (1989) West London Assessment Study: Stage Two: Report on Options. Report for the Department of Transport by Sir William Halcrow and Partners Ltd, Halcrow Fox and Associates, Shankland Cox and Robert Adams, paragraphs 9.4 to 9.9.
Halcrow Fox and Associates (1992) Norwich Area Transportation Strategy: Final Report. Report for Norfolk County Council.
Halcrow Fox and Associates (1993) Review and Specification of Model Elasticities. Report for the Department of Transport by Halcrow Fox and Associates, Accent Marketing & Research, and the University of Leeds, as part of the London Congestion Charging Research Programme.
Hills PJ (1995). What is induced traffic? This issue of Transportation.
Webster FV & Dasgupta M (1991) Land Use and Transport Interactions: Report of the ISGLUTI Study. Transport and Road Research Laboratory Contractor Report 295.
Williams HCWL & Moore LAR (1990) The appraisal of highway investments under fixed and variable demand. Journal of Transport Economics and Policy 24: 61–81.
Williams HCWL & Lam WM (1991) Transport policy appraisal with equilibrium models I: generated traffic and highway investment benefits. Transportation Research 25B(5): 253–279.
Williams HCWL & Lai ITS (1991) Transport policy appraisal with equilibrium models II: model dependence of highway investment benefits. Transportation Research 25B(5): 281–292.
Williams HCWL, Lam WM, Austin J & Kim KS (1991) Transport policy appraisal with equilibrium models III: investment benefits in multi-modal systems. Transportation Research 25B(5): 293–316.
Williams HCWL & Yamashita Y (1992a) Equilibrium forecasts of travel demand and investment benefit measures for congested transport networks. Proceedings of PTRC Summer Annual Meeting.
Williams HCWL & Yamashita Y (1992b) Travel demand forecasts and the evaluation of highway schemes under congested conditions. Journal of Transport Economics and Policy 26(3): 261–282.