Last month, I wrote about my interview with Sara Bronin—professor, architect, attorney, author of Key to the City: How Zoning Shapes Our World, and the planning commissioner who led Hartford’s comprehensive zoning reform. We talked about when the right time is for public input in development processes, and I promised readers I’d be back with more from our conversation.
Bronin and I covered a lot of territory that day, but one thing kept pulling at me afterward: her research on the connection between zoning, transportation, and road safety. Bronin is not just a former planning commissioner; she is a leading expert in land use at every level, including how zoning affects traffic.
Road safety is a passion of mine, and I’ve learned that the link between deadly roads and land use remains unclear to too many people—including our state and local elected leaders.
New Mexico’s traffic fatality rate is the tenth highest in the United States. Last year, KUNM dedicated an hour of its Let’s Talk New Mexico show to dangerous driving, with residents and officials struggling to understand what’s gone wrong on our roads.
Sara Bronin has already written the answer—and it isn’t primarily about enforcement or even driver behavior (although these are important!) but about the laws that determine how far apart everything is.
It’s basic geometry
When I told Bronin about New Mexico’s deadly roads, she wasn’t surprised. She’s seen this before. In fact, she’s published peer-reviewed research on exactly why it happens.
“If you’re wondering why the scientists who work at the Lab are having to drive an hour to get home, it’s really just a matter of basic geometry,” Bronin told me. “If you have a whole bunch of two-acre lots, you’re pushing development farther and farther away.”
Here’s what she means. Through the National Zoning Atlas project, Bronin and her team have shown how in many places—including New Mexico—land zoned for single-family homes is often wasted by requirements for large minimum lots, frequently an acre or more; and, in many districts, two acres or more. In Los Alamos, for example, about three-fourths of residential land is zoned single-family only, much of it mandated to sit on relatively large lots.1
When the rules say each individual house must sit on a large lot, it physically spreads destinations apart. When destinations are far apart, everyone has to drive. When everyone has to drive, crashes go up simply because more miles are driven on dangerous roads.
“The minimum lot size is an issue that maybe seems boring on the surface, but actually has many, many other impacts in other areas,” Bronin said. Road safety is one of those impacts.
The more miles traveled, the more danger
Bronin pointed to a concept well known in transportation research but rarely discussed in housing debates: Vehicle Miles Traveled, or VMT. It’s simple and obvious, but often overlooked: the more miles people drive, the more opportunities there are for crashes.
“If American zoning codes created more mixed-use and more walkable communities, places that people did not need a car to get around, you’d see tremendous benefits from an environmental standpoint, from a safety standpoint, and from a public-health standpoint,” Bronin told me.
New Mexico’s data show the cost of designing for cars, not for people.
According to Los Alamos National Laboratory (LANL), two-thirds of its 18,000 person workforce lives outside the county and commutes. The numbers are similar for other Los Alamos employers because their workers can’t find a house in town either. In one survey, 75% of those commuters said they’d prefer to live closer to work.
Meanwhile, crashes with injuries in Los Alamos rose from 23 in 2017 to 51 in 2023, and there were two fatalities in 2024 during the morning commute.
There is a curious fatalism about this situation, as if Moses had an eleventh commandment: thou shalt liveth far apart and driveth everywhere in single-occupancy vehicles. But our terrible road-safety problem is no act of God. Regulations are the work of humans. And for the most part, it isn’t workers who are choosing these long commutes—those who have written the zoning codes are doing the choosing. So they must bear some of the responsibility for the consequences.
Federal highway standards make it worse
Bronin’s research goes deeper than local zoning rules. She’s written extensively on how federal highway design standards prioritize speed over safety—and how those standards interact with exclusionary zoning to produce what she calls a “deadly” transportation regime.
“The automobile industry is extremely influential in the way that our roads are designed, and in creating the design standards at the federal level, and then at the state and local levels as well,” she said.
In their Harvard Law Review article “Rewriting Our Nation’s Deadly Traffic Manual” Bronin and Arizona State University professor Gregory Shill dissect the Manual on Uniform Traffic Control Devices (MUTCD)—the federal document that shapes nearly every road in America.
One of its core practices is the “85th percentile rule,” which empowers agencies to set speed limits at or below the speed at which 85% of drivers travel in free-flowing traffic. If as few as 15% of drivers are exceeding the posted limit in light traffic, engineers are encouraged to raise the limit to match the behavior of that speeding minority—even when doing so is clearly reckless.
As Bronin and Shill put it, the rule is “perhaps unique in American law in empowering lawbreakers to activate a rewrite of the law to legalize their own unlawful conduct.” Even the Federal Highway Administration has acknowledged that the research used initially to justify the 85th percentile approach “may not be valid under scrutiny,” according to the article.
The human consequences are grim. Safety analyses show that a pedestrian hit at 20 mph has about a 90% chance of survival; at 30 mph, that falls to around 50%; and at 40 mph, it drops to 15%. Yet the 85th percentile rule systematically ratchets speeds upward, toward killing velocity.
As Bronin and Shill put it, the rule is “perhaps unique in American law in empowering lawbreakers to activate a rewrite of the law to legalize their own unlawful conduct.”
As Bronin and Shill write, the MUTCD “establishes a hierarchy of vehicular speed over public safety, vehicular mobility over other uses of public space, and driving over other modes of mobility.”
Their analysis sheds light on something a caller said on KUNM’s dangerous-driving episode last June. Jim from Taos observed: “We have designed our roads and a lot of our streets to be as dangerous as possible; they’re wide, they’re designed for speed.” He was describing exactly the outcomes Bronin warns about—federal speed-first standards filtered through state and local practice, producing roads from Los Alamos to Taos that function perfectly for fast driving and poorly for human survival.
You can’t fix everything with cops and PSAs
During that KUNM discussion, Dan Mayfield, a public information officer for the City of Albuquerque, talked about what they’re trying: road diets, HAWK signals, and protected bike lanes. Albuquerque has adopted a Vision Zero goal of eliminating traffic deaths by 2040.
Jeff Barela from the New Mexico Department of Transportation explained the state’s approach this way: “I think with any traffic safety campaign that we implement, the partnership and collaboration between the educational component and enforcement component is vital,” he said. “But secondarily, if there’s no consequences or there’s no enforcement component to reinforce those behaviors, then our campaigns and our message isn’t as effective.”
Education and enforcement are essential, but Bronin’s research suggests there’s a deeper problem. You can flood the airwaves with PSAs, you can hire more police—but if zoning codes still force people to drive everywhere, you’re treating consequences, not causes.
“Those two are intimately interlinked,” Bronin told me about transportation and land use. “If American zoning codes created more mixed-use and more walkable communities, places that people did not need a car to get around, you’d see tremendous benefits.”
One KUNM caller, Carlos from Albuquerque, captured the limits of enforcement very succinctly: “People drive the speed they feel comfortable, and that depends on the geometry of the road,” he said. “You’ll never have enough police officers to enforce speed limits.”
He was right about geometry. But Bronin’s framework shows it’s not just the geometry of individual roads—it’s the geometry of entire cities, determined by zoning codes that mandate large lots and separate uses.
Zoning is a tool that can be used for good or ill
In Hartford, Bronin didn’t just study these problems—she rewrote the rules.
“Communities can use zoning to help guide what happens in the public right-of-way, including the street,” Bronin told me. “Through zoning, jurisdictions across the country are given power to regulate land use. It doesn’t exempt public rights of way.”
Hartford’s reformed zoning code, for example, has a section dedicated to street design. Streets are classified into types, each with a cross-section that includes not just driving lanes but “amenities for all potential types of users, and not just drivers”—sidewalks, bike facilities, street trees, and transit features, according to Bronin.
Albuquerque has tried similar street-level improvements—road diets, protected bike lanes, and the Albuquerque Rapid Transit (ART) line. These changes can make individual corridors safer. But the Duke City has not summoned the political will to overcome the fundamental geometry problem. When zoning forces destinations far apart, everyone still has to drive, and VMT stays high. The city has put effort into safer street design, but hasn’t put similar effort into getting cars off the road. Land use rules create traffic.
The missing piece: Mixed-use and density
Bronin’s work on land use, transportation, and climate change shows that real transportation safety requires going beyond street-level thinking: you have to change what’s legal to build—and where.
For transit-oriented development to function effectively, you need enough people living near the line—on the order of 10 to 15 homes per acre—to reliably support frequent service. Los Alamos currently has very little development at this scale: we only allow about 5 to 7 homes per acre. (I wrote about this in more depth here.)
Albuquerque, too, is low-density where it shouldn’t be. A Reimagining Albuquerque blog post titled “It Wasn’t the Bus: Why Nob Hill—and Central Albuquerque—Are Struggling to Stay Full” makes the point well:
What makes this even more frustrating is that the UNM area is partially zoned for higher-density development—but only in narrow slivers. Much of the surrounding neighborhood remains locked in low- and medium-density residential zoning, with minimal allowances for mixed-use or multifamily housing. Walk one block off Central and you’ll find a patchwork of restrictions that make it nearly impossible to add new apartments or student housing—despite sitting next to the state’s flagship university and a BRT [bus rapid transit] line.
The result is exactly what Bronin described: infrastructure without the density to support it. People still must drive to reach the transit, then drive home. The bones exist, but the land use doesn’t.
This is the geometry problem Bronin talks about. When neighborhoods block apartments near transit, it’s not just a housing problem—it’s a traffic problem. They’re forcing future residents into cars and onto dangerous roads. According to the same piece from Reimagining Albuquerque, census tracts covering neighborhoods between San Mateo and the UNM area have, since 2010, collectively lost more than a thousand residents—not because people fled, but because nobody’s moving in. Young people can’t find housing they can afford close to jobs, classes, and transit. Fewer nearby residents means fewer customers, fewer eyes on the street, and more workers commuting from farther away on dangerous roads.
When you allow lots of housing near transit, you create genuine alternatives to driving—making roads work better for those who still need to drive.
What New Mexico can do
Las Cruces recently adopted “Realize Las Cruces,” a major overhaul of its development code that legalizes apartments, multiplexes, and accessory dwelling units across most of the city—making it one of the more ambitious zoning reforms in the country. Meanwhile, Albuquerque, Santa Fe, and Los Alamos continue to struggle with procedural gridlock driven by neighborhood defenders who organize to block even modest infill.
Bronin’s framework suggests these aren’t separate problems requiring separate solutions. Housing policy = transportation policy = safety policy.
The thousands of workers commuting to Los Alamos each day represent not just a housing policy failure but also a road-safety crisis. Each of those commutes—many along dangerous routes—results from policy choices embedded in zoning codes that mandate large lots, prohibit apartments, and separate housing from workplaces.
The New Mexico legislature could help fix this problem. By requiring that housing projects meeting local zoning standards receive approval without further discretionary review, lawmakers could let cities keep their rules while preventing small groups from vetoing projects the rules explicitly permit. This is becoming standard practice in states from California to North Carolina, and Bronin and I discussed it in more detail here.
For legislators serious about road safety, this is the leverage point. You can’t fix New Mexico’s deadly commuting crisis one road diet at a time while zoning codes keep generating traffic and long commutes.
What residents can do
When neighbors show up to oppose new housing to “preserve neighborhood character,” they’re not just defending their territory. Whether they know it or not, they’re making choices about other people’s safety.
They’re voting for traffic congestion. They’re voting to extend someone else’s commute. They’re voting to put more cars on dangerous roads.
Bronin’s research shows there’s a different choice available. Her entire career has been devoted to showing cities how to make it.
The comprehensive plan updates happening across New Mexico in 2026 are opportunities to make that choice. Hartford showed it’s possible. Las Cruces showed it’s possible in New Mexico.
Will other New Mexico communities follow? Or will they keep designing for death?
You can read more about single-family zoning in New Mexico, and its side effects, in this piece from Pew Charitable Trusts: “Restrictive Regulations Fuel New Mexico’s Housing Shortage.”
As someone who was on the board of BikeABQ, I wholeheartedly agree. Thank you so much for writing this up.
I agree with all the points that you raise in your article. I would like to add one thing that needs attention-traffic engineer demands based on outdated standards. Until recently, Santa Fe traffic engineers were using federal highway traffic manual standards on local streets. Thanks to Erick Aune’s (Director of the MPO) foresight and vision, we hired a consultant to help us create standards that fit the context. First it was applied on how the traffic analysis was done, now Erick is taking it a step further and is creating a street design guide that will be enforced through the Land Development Code. I submit that it is a multi-pronged approach-zoning, density, and context-sensitive street design. A bit of traffic and inconvenience can be a good thing-people then consider other modes of transportation. Sorry for the rant-it’s so important to me to think about people first!