Tag Archives: equity

Is Fare Free Transit Just?

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.

Unexpected Data Bias in Smartphone Trace Data

This study, a joint study with Professor Amanda Stathopoulos‘ group, explores the impact of shifting device representation bias in smartphone tracking data collected before and after Apple’s 2021 privacy updates on user location tracking. It demonstrates that privacy regulations can significantly and unexpectedly affect the quality of these data, which are crucial for decision making across governmental, corporate, and academic institutions worldwide. The research also corrects misconceptions about representation bias previously speculated in the literature. Overall, the findings equip users of location-based device data with a better understanding of potential pitfalls, enabling them to anticipate the changes caused by the evolving regulatory landscape and to devise appropriate coping strategies. This finding is contrary to popular concerns about the under-representation of low-income populations in LBS data.

Download the preprint here and read the abstract below:


As smartphones become ubiquitous, practitioners look to the data generated by location-tracking services enabled on these devices as a comprehensive, yet low-cost means of studying people’s daily activities. It is now widely accepted that smartphone data traces can serve as a powerful analytical tool for research and policymaking. As the use of these data grows, though, so too do concerns regarding the privacy regulations surrounding location tracking of private citizens. Here, we examine how Apple’s tightened privacy measures, designed to restrict location-tracking on their devices, affect the quality of passively generated trace data. Using a large sample of such data collected in the Chicago metro area, we discover a significant drop in iOS data availability post-privacy regulations. The results also reveal a surprising puzzle: the reduced tracking is not uniform and contradicts customary concerns about the under-representation bias of low-income population. Instead, we find a negative correlation between device representation level and income, as well as population density. These findings reframe the debate over the increasing reliance on smartphone data, highlighting the need to understand evolving issues in tracking, coverage, and representation, which are essential for the validity of research and planning.

Ethics-Aware Transit Design

In this paper we proposed a corridor transit design model that places accessibility and equity at the center of the trade-off. By guiding transit design with ethical theories, it promises to improve vertical equity. We reviewed and examined four different ethical principle but were focused on the utilitarian principle (the status quo) and John Rawls’ difference principle (a form of egalitarianism). The main findings from our analysis of the design models are summarized as follows.

  • When the transit service is homogeneous in space, the utilitarian design model and the egalitarian design model are mathematically equivalent. Thus, they always produce identical designs for all forms of the opportunity distribution.
  • With supply heterogeneity, the egalitarian design has a prominent equity-enhancing effect, whereas the utilitarian design tends to exacerbate inequity, especially in presence of large innate inequality.
  • Correcting innate inequality by applying the egalitarian principle often entails interventions that appear more “discriminatory” than the status quo. Whether such distributive measures are justified, the appearance of unfairness can be met with skepticism, if not outright opposition, from the general public.
  •  Our ability to promote equity is restricted not only by the resources available but also by the structure of the problem at hand. The difference principle is useful because it defines the upper limit of equity that we may strive to reach but should not exceed.

It is worth recalling the egalitarian design based on the difference principle tends to reduce the total accessibility of all residents, compared to the incumbent design regime of utilitarianism. When innate inequality is large, the loss of accessibility can be substantial, up to 40\% according to our experiments. This, of course, is hardly a surprise, given the primary concern of the difference principle is the distributive justice, not the total utility. One thing is clear though: the benefits to the most disadvantaged could come at a hefty price to society writ large. Steven Dubner, the host of the popular podcast Freakonomics, likes to quip,

Economists know the price of everything but the value of nothing.

No doubt the same can be said about many if not most engineers. In some sense, our study constitutes an attempt to price social values in engineering practice. To be sure, these values are priceless to many an advocate, who would be quick to point out that the obsession with pricing everything is precisely what got us here in the first place. However, understanding the consequence of imposing certain values in engineering systems is still a crucial task, if only because we always need to secure public support or determine affordability.

The work is partially funded by Northwestern University’s Catalyst fund and NSF’s Smart and Connected Community (S&CC) Planning
Grant.  A prerprint of the paper may be downloaded here.