A conceptual framework to formulate transportation network design problem considering social equity criteria

In recent years, researchers have developed new methods to measure how transport decisions affect different groups of society. An example is the distribution of impacts (benefits and costs) from roadway investments, and the degree that the results are considered equitable (also called fair or just). Such decisions affect people’s ability to access services and activities, and therefore their economic opportunities and development. This study suggests ways of incorporating social equity measures in transportation network planning. It describes various equity impacts that can result from transportation planning decisions, discusses various social equity concepts and theories, reviews previous attempts to incorporate equity considerations into transport networks modeling, and suggests a framework for simultaneously optimizing network design and achieving social equity objectives. According to this framework, network design can be formulated using bi-level integer programming models corresponding to seven major social equity approaches along with the classical approach of “Total Travel Time Minimization.” An accessibility variable is used as the distributable benefit. This approach is more comprehensive and flexible than previous equity impact models. The proposed framework can be used to evaluate and optimize the equity impacts of various infrastructure investment decisions.