Transport policy appraisal with equilibrium models I: Generated traffic and highway investment benefits

In a series of three papers the authors investigate within an equilibrium framework the magnitude and composition of benefits arising from the various responses of travellers and operators to transport investments. In particular, they determine both analytically in simplified models and numerically in network representations, the extent to which the benefits to generate traffic may be more than off-set by the addtional congestion inflicted on other road users. In this paper the authors adopt a uni-modal network to appraise a variety of highway schemes and explore the sensitivity of user benefits to: the demand model specification; the inherent elasticity parameters; the level of congestion in a reference network; and the policies selected. The implications of the results for the methods of investment appraisal in urban and nonurban contexts are considered.