Can traffic congestion be managed without compromising social equity?

Abstract

Managing road traffic congestion through Travel Demand Management (TDM) policies can improve traffic performance. However, the impact of these management policies on social equity remains unclear. An important area that demands further investigation in applying TDM policies, particularly with push effects, is addressing social equity externalities. This study investigates the impact of integrating three push-pull Travel Demand Management policies on two seemingly contradictory objectives: reducing traffic congestion and increasing social equity. A qualitative System Dynamics approach is used through Causal Loop Diagrams, combined with Decision Making Trial and Evaluation Laboratory approach. The Causal Loop Diagrams are validated through a three-round Delphi approach validation involving expert participation from six Western European countries. Three policies are modeled, two with push-effects and one with pull-effect, both individually and collectively to examine their dynamics and the effects of policy integration. The results show that integrating push-policies strongly influences variables that lead to short- and long-term reductions in traffic congestion. In contrast, integrating pull-push policies reduces externalities on socially disadvantaged population groups. The pull-TDM policy introduces an additional leverage point that reduces traffic volume while mitigating social equity impacts caused by other leverage points and feedback loops in the model. The findings of this study improve the understanding of the impacts of integrating mixed push-pull TDM policies to reduce traffic congestion and social externalities. This aids the future design of integrated policy frameworks with other policies that can address the technical aspects and social dimensions of urban transport systems.