Abstract:

Public transit plays a central role in shaping urban mobility, yet its design is deeply intertwined with broader transportation policies—particularly pricing, taxation, and subsidy schemes that influence traveler behavior and sustain system operations. At the same time, transit systems are expected to achieve multiple, and often competing, objectives, including congestion mitigation, accessibility provision, and affordability for disadvantaged populations. These objectives reflect underlying government priorities, which are implicitly guided by normative moral principles.

In this seminar, I present a unified transportation economics framework that jointly designs transit services and transportation policies while endogenizing traveler choices. The framework enables a systematic evaluation of both efficiency and equity outcomes under two normative principles - utilitarianism and egalitarianism. I illustrate the framework through two applications addressing emerging challenges in urban transportation systems. The first examines optimal fare policy, with a focus on discussing whether and under what conditions fare-free transit is justified. The second investigates the impacts of rising telework in the post-pandemic era on public transit systems, and discusses policy interventions to mitigate potential undesirable distributive effects.

Bio:

Tianxing Dai is a Ph.D. candidate in Civil and Environmental Engineering at Northwestern University. He earned his Bachelor of Science degree with a minor in urban and regional studies from University of California, Los Angeles. Tianxing's research focuses on transportation system modeling, urban mobility, and transportation policy design and planning, with particular emphasis on integrating large-scale mobility data, economic theory, and emerging AI methods to understand and improve the evolving transportation systems.