Using activity-based models and the capability approach to evaluate equity considerations in transportation projects

The capability approach (CA) is a theoretical framework that emphasizes the moral significance of individuals’ capability to achieve outcomes that they value and have reason to value. It focuses on the actual opportunities that people have given their personal and social circumstances. This approach is grounded in the attempt to address fundamental deficiencies of the utilitarian approaches to welfare economics and to raise equity issues. In this work, we explore CA in the context of the transportation field. We develop a new measure, “Value of Capability gains” (VOC), designed to account for both efficiency and equity considerations as the key benefits taken into account in a Cost Benefit Analysis. We utilize activity-based models to assess travelers’ capabilities under different transportation improvement scenarios. By using the activity-based accessibility measure to reflect individuals’ abilities to reach alternatives that are potentially achievable, in accordance with the CA approach, the principle of diminishing marginal utility can be activated and applied to accessibility as a quantity of good or service—so that the more alternatives available to the traveler, the smaller the marginal benefit from an additional alternative. We use the VOC measure to examine different transportation scenarios in a simple synthetic case study, demonstrating that this new measure better accounts for equity.