Early this month, a Boston transportation planner and bike-safety advocate was fatally struck while cycling in an unprotected bike lane. Her loss has catapulted questions about the policy evidence for—and politics of—street safety back into the spotlight. 

We spoke with Justin de Benedictis-Kessner, the Emma Bloomberg Associate Professor of Public Policy at Harvard Kennedy School, whose research focuses on urban politics and policy, including transportation, to understand why bike lanes generate such significant political conflict in Boston and cities nationwide.

Q: Boston transportation planner and bike-safety advocate Louisa Gag was killed while cycling in an unprotected bike lane. How often are people killed by cars and trucks, and what steps have cities taken to prevent accidents? 

Louisa Gag’s death was tragic. It also is one of nearly 40,000 traffic-related deaths that occur in the United States each year. These kinds of deaths happen quite frequently in American cities, especially in comparison to our global peers. These numbers include people driving cars, as well as pedestrians—people walking on sidewalks and crossing streets—and cyclists like Louisa Gag. Traffic violence sadly affects all types of people trying to get around their cities.

Cities often start to try and make their streets safer and encourage sustainable transportation—as Boston did under Tom Menino in the late 2000s—by adding bike lanes to their streets—simply painting a lane at the side of the road to designate where cyclists should ride and drivers should not drive their cars and trucks. 

It’s a first step towards trying to get everyone to understand where different types of road users should go on city streets. However, these painted lanes are basically “generation 1” of how cities can do this. Just like cell phone technology has advanced from flip phones with numeric keyboards to smartphones, transportation safety has advanced its technology. There’s been a lot of research from around the world—including from the Federal Highway Administration—showing how bike lanes are safer for everyone when they are “protected,” by adding some form of physical, vertical separation barrier between the bike lane and car lanes. Vertical separation can be concrete curbs, plastic flexible posts (“flexposts”), or even parked cars.

Q: Cities often build unprotected lanes as an interim step toward protected ones. What does research tell us about these options? 

Research shows us that protected bike lanes are easier for everyone to understand, whether they’re driving, biking, or walking. Everyone has a clearly delineated space on the road, so it’s less likely that people will bump into each other as they travel throughout a city.

But there are also secondary safety effects: First of all, protected bike lanes often help break up a street for pedestrians so they’re not trying to cross a bunch of car lanes at once. Instead, they have breaks in crossing between a narrower bike lane, then a couple of car lanes, and then a narrower bike lane again. That often makes crossing way less frightening for both children and adults trying to cross the road.

Second, because protected bike lanes often take up more space on the road than simple painted or unprotected bike lanes, they also often involve narrowing the car travel lanes. This causes people driving cars to slow down because of the perceptual effects of a narrower lane (that’s why highway lanes are wider: it enables people to drive faster). As a result of these protected bike lanes and narrower car travel lanes, people drive slower in cities. This is actually safer for everyone—car and truck drivers, pedestrians, and cyclists—because car crashes are much more dangerous and much more likely to be fatal when people are driving faster in cities.

Q: Why don’t cities build more protected bike lanes, despite the benefits? 

Cities keep building unprotected or painted bike lanes for many reasons. One barrier is administrative and comes from the federal guidelines for street signage and markings, called the Manual of Uniform Traffic Control Devices (MUTCD), which local transportation planners follow in their street designs. Up until the most recent edition, which was only released in 2023, the big priority in the MUTCD was getting cars through streets at optimal speeds, and it didn’t fully list as “standard” some of the proven safe designs like physical lane separation that is key to building protected bike lanes. So just like with smartphones, not everyone was on the cutting edge of technology with protected bike lanes because our rulebooks hadn’t yet made new technology the standard approved infrastructure.

But protected bike lanes are also pricier than painted bike lanes since they require items like flexposts or concrete curbs. So, cities sometimes might keep adding painted lanes because they don’t see it as worth the added cost—just like how some people might think the benefits of a smartphone aren’t worth the added price tag.

Finally, and perhaps most importantly, some cities don’t add protected bike lanes because they get pushback from residents about some of the secondary effects of those lanes. Protected bike lanes change the way things look on the street, they take up more space on the road (sometimes requiring the removal of other things like parking), and they sometimes slow down traffic because of the known safety benefits of slower speeds for crash fatalities. For some city leaders, those are tradeoffs they don’t make in the pursuit of safety, especially when they have a vocal group of people opposed to them.

Q: A 2025 Boston Magazine piece was titled “This Bike Lanes Story Isn’t Really About Bike Lanes.” What issues get projected onto bike lane debates?

What it comes back to is that—like with many issues where political leaders face tradeoffs—people see the visible “winners” and “losers” after a policy change. On the one hand, there are real differences in what people want from their governments, and those divides can be partisan, like they often are at the national level, and as some of my research has shown. But they can also be based on other characteristics of city residents: homeowners can disagree with renters; people who drive cars daily to work can disagree with those who don’t drive to work but walk, use public transit, or bike—which is the majority of people in places like the Boston area.

We often bemoan partisan polarization at the national level because it leads to partisan vitriol, dysfunction in Congress, and inaction around important policy issues because of a refusal to compromise. People’s lives suffer because policy problems aren’t getting addressed by their representatives.

I think bike lanes are a perfect example of where we can see the downsides of polarization at the local level, too. Because there are strong opinions on both sides, and political leaders may avoid making decisions that might look like they’re favoring one side or the other, we often end up with policy inaction. Instead of acknowledging a real policy tradeoff, leaders can sometimes decide to not make changes. At the end of the day, that means keeping the status quo, which in so many of our cities is choosing unsafe streets that lead to tens of thousands of people dying each year.

Q: Bike lanes take up a tiny fraction of cities’ street networks, yet they seem to generate more heated conflict than other infrastructure issues. What makes them so controversial?

Political opposition to bike lanes happens because of those tradeoffs associated with the construction of bike lanes. Just like with any policy decision, adding bike lanes requires leaders to choose one priority over another. In the case of protected bike lanes, that is usually prioritizing safety of all road users over the fast driving and easy availability of parking that people might be used to in their cities.

Yet many city residents don’t see the benefits of those bike lanes, especially when they come with those costs that I just mentioned. It’s easy to see the costs when there’s parking removed to add protected bike lanes. Or when there are fewer lanes for car travel.

Justin de Benedictis-Kessner headshot.
“Instead of acknowledging a real policy tradeoff, leaders can sometimes favor doing nothing. … [T]hat means keeping the status quo, which in so many of our cities is choosing unsafe streets that lead to tens of thousands of people dying each year.”
Justin de Benedictis-Kessner

But it’s really hard to see the benefits: by design, bike lanes are never going to be full of stopped cyclists in the way that car travel lanes are nearly always going to have car and truck drivers visibly stopped at a stoplight, because cars and especially trucks simply take up a lot more space than bikes. And it’s nearly impossible to see some of the invisible benefits of bike lanes: people don’t necessarily associate driving at a lower speed in a city as “safer” in their minds, so the added safety isn’t visible at all to the casual observer. Instead, it appears to many people that their city is prioritizing one group of people (people riding bikes) over another group (people parking or driving cars).

In contrast, when people see repaving happen on a street, it’s obvious that the road is now smoother. And the direct effect of a smoother road is obviously better for everyone, while the benefits of bike lanes for everyone (in the form of safer streets) aren’t visible, and instead it looks like they’re just benefiting people riding their bikes.

Q: Boston Mayor Michelle Wu ran on a street-safety agenda, slowed it before her reelection, and by most accounts has kept that slower pace since her reelection. What does that say about the political durability of a “mandate” once implementation starts costing parking spots?

While you might call the eventual pushback to Mayor Wu’s street safety agenda evidence that she didn’t have a durable mandate, I’d argue that picture is inaccurate.

Like many political leaders, Mayor Wu was confronted with the fact that many people opposed a signature campaign issue that she staked her campaign on, and those opponents are vocal, and only got more vocal once she took office. Research has shown how the political process includes many more people who are wealthier, older, white, and homeowners in local deliberative processes around housing policy. People who show up to meetings to discuss housing policy in local government don’t broadly represent the overall populations in cities and towns.

That same dynamic happens with transportation policy in cities, too: the people who show up to meetings and proactively contact city government about bike lanes don’t represent the average person in cities like Boston. As a result, political leaders like Mayor Wu often hear a very biased picture of what residents in their city want. Instead of hearing from a representative group of their constituents, they hear from the loud and politically empowered population who shows up to meetings or writes to them. Of course, there are some simple solutions to this problem if leaders want to actually know what their residents want. For instance, they can conduct representative surveys, or they can target in-person outreach to populations that have been under-represented in past decision-making processes. Those steps to remedy the biased nature of the status quo political process in cities require a little bit of creativity and initiative. If a mayor wanted to gauge how solid their mandate is to address problems like street safety, I’d encourage them to look at two things: their election results and their representative polls.

Q: The Trump administration has canceled or redirected bike and pedestrian infrastructure funds, including grants to Massachusetts, saying they are misallocated or “hostile to cars.” Is federal bike-lane politics a new front, or is it just nationalizing a local-level fight?

The Trump administration is making prioritization decisions just like how city leaders do, but making it more openly. President Trump quite clearly wants federal money to go towards car drivers and not towards pedestrian and cycling infrastructure because of that dynamic I mentioned earlier: it appears like car drivers are “losing” when money funds infrastructure improvements that visibly create separated bike lanes or expand crosswalks at the expense of space for parking or driving cars and trucks. This is exactly what the Trump administration means when they say an infrastructure change is “hostile” to cars.

But again, that’s ignoring the benefits to all road users that come from street safety improvements. And it’s also ignoring that—while there has been a decrease in traffic-related fatalities in the years following the pandemic, the number of traffic fatalities for people outside cars has actually been rising or steady: federal data show that over 8,000 pedestrians and cyclists were killed in crashes in 2024. We can’t fix those problems with better airbags, or larger crumple zones in cars, because those types of technology improvements benefit the people inside the car but not the people outside the cars who also can get injured and killed in car crashes. The Trump administration, in many policy areas, sees policy choices as binary and zero-sum: they’re helping one group of people at the expense of others. The way this administration has taken a position on bike and pedestrian infrastructure improvements is new, because these are areas that have previously been left up to state transportation departments and cities. Those state and local governments have been much more willing to see infrastructure policies as having broader consequences for safety, rather than just dividing people into winners and losers. 

Q: Minneapolis, Baltimore, Detroit, Philadelphia, and San Francisco have also had bike lane battles. What patterns repeat across cities, and what, if anything, is different about Boston?

What’s happening in Boston is basically the same as what’s happening in other cities—an unrepresentative political process and a hesitation by political leaders to boldly face tradeoffs and defend their choices. It’s a similar political dynamic in Boston as it is in other cities. In some of my ongoing research, I’ve been collecting data on what people in cities across the country think about various local government policies, including bike lanes, for the last couple of years.

The data show that in many cities, majorities of the public support infrastructure improvements like bike lanes, but also policies such as automated speeding or red light cameras, or adding bus lanes—all of which can make streets safer and provide more transportation options. Of course, the levels of support vary across different cities. And opponents of these policies in every city might see these policies as “hostile to cars”—just as Trump administration officials see these policy changes as zero-sum decisions that set up clear winners and losers. But again, that’s ignoring the secondary effects of those policy changes that can benefit all road users and make cities safer for everyone—people driving, walking, and riding bikes.

Helping people see those broader consequences of policy choices is what politics is all about, though: political leaders both follow mandates from voters and convince their constituents of the policy options that they think of as most beneficial in the long term. Just as in politics more broadly, mayors who exercise leadership in policy choices about bike lanes have to balance both following and leading their constituents in this policy area.

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Photograph by Barry Chin/The Boston Globe/Getty Images
Caption: People gather for a memorial vigil on July 10, 2026, at the area where Louisa Gag was fatally struck.

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