Citation

Metz D. Proc. Inst. Civ. Eng. Transp. 2006; 159(4): 159-163.

Affiliation

Centre for Transport Studies, University College, London, United Kingdom

Copyright

(Copyright © 2006, Institution of Civil Engineers, Publisher ICE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

The value of accident savings is commonly an important element of the economic benefit of a road improvement scheme, as estimated by standard cost-benefit methodology. The other important economic benefit is supposed to be the value of travel time savings. However, average travel time has remained constant for many years, which suggests that in the long term the benefits of road improvements are taken in the form of additional access to more distant destinations at higher speeds, rather than in the form of time savings. Such additional travel will result in extra accidents, which are not adequately taken into account in conventional economic appraisal methodology. The value of such extra accidents has been estimated for a number of UK highway schemes. On average the value of these accidents exceeds the value of the accident savings claimed for the schemes. Road improvements designed to reduce accidents therefore need to avoid increasing traffic speeds.