Earlier this year, Governor Maura Healey made a promise to root out systemic racism from “every corner of government.” But a sweeping investigation is shedding light on recurring racial discrepancies in traffic stops. 

The data for all Massachusetts traffic stops collected between 2014 and 2022 reveals that, on an average day, Black drivers are 2% more likely to be stopped by a police officer, up to 6% for Latino drivers and 3% for all minority drivers combined. 

The previously unreleased data is raising pressing questions, including ones about whether the data itself is skewed; Massachusetts police have consistently mislabeled men with Hispanic last names as white on traffic citations, which would complicate further efforts to address police bias. 

Matthew Ross, an associate professor of public policy and economics at Northeastern University, who assisted with the study’s analysis and conducted his own meta-analysis, joined All Things Considered host Arun Rath to discuss the findings. What follows is a lightly edited transcript.

Arun Rath: To kick us off, can you give us an abstract of the study and its findings?

Matthew Ross: Absolutely. We analyzed about 4.3 million traffic stops that resulted in a citation, and the primary test we used to look at the data is something known as the “veil of darkness” or a solar visibility analysis. What that effectively does is it relies on seasonal variation in the timing of sunset throughout the year, as well as the discrete change in the timing of the sunset right before and after daylight saving time.

Effectively, the test is based on the idea that during daylight hours, when the sun is out, if police are inclined to discriminate against minority motorists, they’ll be marginally better able to do so during daylight hours.

The reason we use this test or a series of complicated tests like this is due to the fact that, unfortunately, there’s not readily available data on the driving population of who’s on the road at any given time, at any given location. So, researchers like myself turn to these quasi-experimental tests to identify discrimination.

Rath: Let’s talk about some of the concerns with the data. As we mentioned, it’s the police who are essentially in charge of determining the race, so there’s the charge that they’re skewing the data by marking a significant amount of Hispanic and Latino people as white when they’re stopped.

Ross: I think that’s right. I mean, one of the big concerns I think that has come to light as part of the USA Today investigation and my own work with the data is [that] not only does it look like that is happening in some departments just across the board over and over for years at a time, but it’s also concerning that the analysis and the follow-up in the entire reporting procedure in Massachusetts is handled by EOPSS, which is the Executive Office of Public Safety and Security here in Massachusetts. So, it’s basically, effectively, that the police are in charge of policing themselves in looking at this data.

Rath: Are there ways to be able to use that to read this data in a way that could be more reliable? Or are there just more data points that we need to be able to understand?

Ross: Well, I think that’s a great question, right? There are a couple of dimensions to that that I think are really important. One is that Massachusetts released its first analysis of traffic stop data, and it’s a much shorter tranche of data over a shorter period of time than what I looked at in my study. It was just in 2020.

The analysis that the state released effectively said that they didn’t find discrimination, and there are a number of shortcomings with that analysis. But without going through the specific details, I think the larger issue really is that the way that the state has attempted to do this is just really sort of a non-transparent process. I often hold up states like California and Connecticut, which are really at the forefront of doing these types of traffic stop studies and really putting in place an early warning system for police discrimination.

The way that states like that have approached it is that they have formed advisory boards that consist of members from the policing community, legislators, the executive branch and members from the advocacy community and organizations like the ACLU. And they have people like myself—academics—that work on this issue and do research on discrimination. Basically, everyone sits at the table, and it’s a public process of how and why the tests that are used are being used, all the assumptions that are going into things.

The data is typically made public. In Massachusetts, that’s not how this process has been, which is why my colleagues at USA Today filed of Freedom of Information Act request to get access to the data and a larger tranche of the data because, last year, with the passage of the seat belt law in Massachusetts, there was a component of it which was to produce this traffic stop study.

Really, everything associated with it has gone on, for the most part, behind closed doors. I think what’s been disappointing about the way the process has gone in Massachusetts is that there’s actually a fair amount of federal money available to fund the data collection and the analysis through the Department of Transporting in what’s known as Section 1906, which was the original section of the transportation bill that funded this.

But instead of actually going through and meeting the criteria and getting the federal money for the study, Massachusetts has put up state taxpayer dollars to fund this study. I think, largely, one of the big reasons that has happened is because I think Massachusetts has been reluctant to make the data public and really wanted to have a firm grip on how exactly the data was used and analyzed.

Rath: It’s fascinating to hear you talk about practices in other states beyond things like transparency. Are there other areas that are instructive for us here in Massachusetts or other practices that we could adopt to help us get some more clarity on this?

Ross: I think one of the big shortcomings of the data that’s currently collected by the RMV is it only involves traffic stops that result in a citation. You know, I’ve worked across the country on similar disparity studies and for organizations like the U.S. Department of Justice, and one of the big things that I’ve observed throughout my career is that there’s typically a large share of traffic stops that only result in a warning, right?

[In] states that I’ve worked in recently—Connecticut and Rhode Island—almost half of their traffic stops in any given year result in either a verbal or written warning. Right now, Massachusetts doesn’t actually track those stops at all. To give you the full history, at one point, Massachusetts did actually track those stops, and it occurred in the same system that they track the traffic stops that only result in a citation.

It’s actually not clear to me—and, I think, to a number of other people that have been involved in this—why Massachusetts stopped collecting traffic stops that resulted in warnings. So, I think that would be a big one: to pass a law that requires every traffic stop to have a document associated with it. Even if it’s a warning, it’s a written warning that then gets entered into the same system at traffic stops. Texas just passed a law a few years ago that banned undocumented stops across the state. I think that would be a really important first step.

And then, the second is to make the data publicly available. You know, it shouldn’t take a group of journalists’ repeated Freedom of Information Act requests to get their hands on data like this. I would think it should be something that is out in the public sphere that anyone has the right to find out what their local law enforcement agencies are doing with their tax dollars.