Tag Archives: modeling

Recent research

How our means and values shape transit policy

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Few topics in urban mobility spark as much debate as fare-free transit (FFT). On one side, advocates argue that eliminating fares can guarantee the “freedom to move”, boost ridership, and make cities more sustainable. For example, Boston’s mayor Michelle Wu, a big fan of FFT, has implemented a limited FFT program in the
city. The idea also featured prominently in the platform of Zohran Mamdani, who has launched a closely watched bid
for the New York City mayoralty.    On the other, skeptics worry about overcrowding, misuse, and—above all—how to replace the revenue that keeps buses and trains running. Behind the heated arguments lies a deeper question: how do our moral values and financial means shape the “best” transit fare policy?

In our new study, How our values and means shape optimal transit fare policy, we set out to answer that question with a rigorous modeling framework. We designed a system that can evaluate not just the economics of different fare options—ranging from full-fare-free (FFF) to partial discounts to today’s standard fares—but also their equity implications. The model captures real-world features such as the “zero-price effect” (the psychological boost of free services), the cost savings from removing fare collection, and the operational dynamics of running a large transit system.

Applied to Chicago, our model led to some interesting findings. When money is plentiful, making transit completely free can indeed be both efficient and fair. But under tighter budgets, targeted discounts often do more to help low-income riders while keeping the system financially sustainable. Perhaps counterintuitively, we also found that giving planners unlimited resources doesn’t always lead to better outcomes—sometimes moderate constraints produce solutions that more people would support.

As cities everywhere grapple with post-pandemic ridership losses and strained finances, these findings matter. Fare policy isn’t just a technical choice—it reflects what we value as a society and how much we’re willing (and able) to pay to uphold those values.

Read the full preprint here.

Recent research

Is Fare Free Transit Just?

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I became interested in fare free transit since  Michelle Wu was elected the Major of Boston. She was the first female Asian major of the city, though her reputation as a disciple of Elizabeth Warren, the liberal firebrand in the U.S. senate,  probably overrode her other identities.  Among many of her agenda items was fare free transit (FFT), which caught my attention  not because it is especially progressive, but because it is a transit policy, which I happen to know something about.  Another source of inspiration for this paper came from Steven Dubner’s podcast on the subject a couple of years ago, which is entitled “Should Public Transit be Free”.

I shared the preprint with my department chair, Prof. Kim Gray, who is an environmental engineer but has a broad interest in anything related to sustainability and climate change. She was impressed and asked her assistant, Miss. Gina Twardosz, to write a news article to be posed on the department website. If you don’t want to read the paper itself, here is the link to that article. The abstract follows.

Abstract: Using a stylized transit design model, this study examines fare-free transit (FFT) through the lens of distributive justice. We pose a direct question: Is FFT just according to John Rawls’s theory of justice? Specifically, is it compatible with the resource allocation that maximizes the utility of the most disadvantaged travelers? We compare this egalitarian principle with a utilitarian one, which asserts that an allocation is optimal when it maximizes the total utility of all travelers. FFT is of course not free. In the absence of farebox revenue, a transit system must either cut services or turn to alternative sources, such as local dedicated taxes and fees levied on drivers. Thus, our model incorporates both finance and operational decisions, and captures the interaction between traffic congestion and travelers’ income level and mode choice. Using a case study built with empirical data in Chicago, we show that fare is not the first choice under either moral principle. For the egalitarian, the most desirable funding source is the driver fee, whereas taxation is preferred by the utilitarian. It follows that FFT can be both just and utility-maximizing, if one is allowed to raise taxes and charge drivers with impunity. However, as the flexibility in finance diminishes, so does the appeal of FFT. In such cases, the proposed model serves as a decision-support tool for finding sensible compromises that address the varied interests and ideologies at play. For example, it reveals that at the current tax rate of about 1% in Chicago, the Rawlsian egalitarian can justify FFT only if drivers pay about $1,800/year to fund transit, which amounts to about 18% of an average U.S. household’s driving cost.