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

TLDR

Growing interest in equity in transport planning has led to criticism of the dominant cost‑benefit analysis methodology. The study investigates the importance of travel time savings in transport project appraisal and examines whether replacing them with accessibility gains can mitigate identified equity concerns. The authors identify five equity effects of using travel time savings in CBA and explore whether substituting them with accessibility gains can address these effects. They find that projects serving majority populations outperform those serving disadvantaged groups in CBA, that only two of the five equity effects are mitigated by accessibility gains, a third can be partially mitigated by diminishing marginal returns, and overall accessibility gains alone cannot resolve all equity issues.

Abstract

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.