Travel time savings, accessibility gains and equity effects in cost-benefit analysis

The growing interest in the equity dimensions of transport planning has resulted in increasing criticism on the dominant assessment methodology of transport projects: cost-benefit analysis (CBA). In this paper, we focus on travel time savings, given their importance in the assessment of transport projects and the sometimes fierce equity-related citicism on their inclusion in project appraisal. We identify five equity effects related to the use of travel time savings in CBA. Each of these equity effects implies that transport projects serving the majority population are highly likely to perform better in CBA than comparable projects serving disadvantaged population groups. We subsequently explore whether the replacement of travel time savings by accessibility gains can address the identified equity effects. We observe that this only holds for two of the five equity effects, while a third effect can be mitigated through the introduction of the notion of diminishing marginal return in the valuation of accessibility gains. We conclude that the mere introduction of accessibility gains is in itself insufficient to address all equity effects related to the application of travel time savings within the CBA framework.