Abstract
A single mode equilibrium model of a transport system is used to investigate the difference between user benefits arising from highway policies when computed under fixed and variable demand, the latter allowing for traffic generated by a project. The dependence of this difference on: the demand elasticity; the initial level of congestion; the variation of user costs with traffic flow; and the policy itself, is explored both analytically and numerically. The central focus of the investigation is the extent to which the benefit to generated traffic is outweighed by the disbenefit inflicted on existing road users through increased congestion. The implications of the results for road appraisal are assessed. (Author/publisher).