Why Do We Keep Widening Highways If It Doesn’t Reduce Traffic?

IRA FLATOW: This is Science Friday. I’m Ira Flatow. Have you ever been stuck in traffic? Well, maybe you are right now, and you had the thought, if only this highway was a little wider so it could fit more cars. Well, you aren’t alone because many states have been expanding their highways across the country for decades.

New York Governor Kathy Hochul recently announced a $1.3 billion project to expand one of the state’s highways for a whopping six-minute travel savings. Other widening projects are underway in states, including Texas, California, and Maryland. In 2022, federal, state, and local governments in the US spent $127 billion on highway construction. These DOTs say expanding highways is necessary to reduce congestion, especially in areas with growing populations and to encourage economic development.

But you know what? Decades of research shows the opposite effect. When highways are expanded, the travel time actually increases. When more lanes are added, people just clog up the new ones. So how does this happen? And why do we keep expanding highways, even though the research says it doesn’t work? Here to explain the science behind highway widening and how some states are actually rethinking their approach to traffic is Megan Kimble. She’s a journalist and author of the book City Limits, Infrastructure Inequality and the Future of America’s Highways. She’s based in Austin, Texas. Welcome to Science Friday.

MEGAN KIMBLE: Thank you for having me.

IRA FLATOW: Lots of highways in Austin, right?

MEGAN KIMBLE: Lots of highways. I’m one mile from I-35 right now.

IRA FLATOW: Well, let’s get to the point. It does seem logical that if you want less congestion, you just widen the road. But that the data shows that widening actually makes traffic worse, right?

MEGAN KIMBLE: Yeah, it’s certainly intuitive. Like you said, if you’re sitting on a highway in traffic, you think, one more lane will get this traffic flowing more quickly. But yeah, it’s actually been well understood for decades that when you add capacity to a highway in the form of new lanes, more cars will rush to fill up that capacity. So that was first articulated in 1962. So just a few years after the interstate highway program began, an economist looked at all these new highways that were being built in American cities and saw that as lanes were added, as capacity was added, the total traffic was increasing.

And this is because travel is a good like any other. It follows the rules of supply and demand. So when you increase supply, demand also increases. So people change their behavior. They maybe move farther from their job and they take on a longer commute because they think they can get there quicker, or they take more discretionary trips, so they go to the grocery store three times, instead of one time. And overall, traffic volumes increase. So the sort stated goal of fixing traffic congestion by adding lanes fails. In project after project, city after city, when highway departments widen, highway travel times actually increase.

IRA FLATOW: But states are also talking about climate goals. We’re going to reduce smog and pollution and greenhouse gases. But more cars are just the opposite. When you widen the highways, you’re having an environmental impact.

MEGAN KIMBLE: Yeah, you’re measurably increasing greenhouse gas emissions. A stat I found when I was reporting my book that absolutely floored me is that on-road emissions in Texas, so the emissions generated by our cars and trucks, account for half a percentage of total worldwide carbon dioxide emissions. So like the highway expansions that I profile in my book, whether those go forward will have a measurable impact on global climate emissions. Every one of these highway expansions contributes to that number.

There’s been a lot of research lately that shows that highway widenings are the number one lever for states to pull to either reduce or increase their greenhouse gas emissions. So you have a lot of governors saying, we are committing to ambitious climate goals. And then their state DOT are funding highway widenings.

IRA FLATOW: Can you point to any benefits of highway expansion?

MEGAN KIMBLE: You certainly can allow more cars on the highway. So you do, in fact, increase the total number of people that can drive on a road. If you expand something from two to four lanes, more cars fit on that road. But I think the question is, do we want to encourage driving? Do we want our public policy decisions and public funding to be spent in such a way that it encourages people to drive?

So the highways enabled the growth of the suburbs. They allowed people to buy more affordable housing out in the fringes of cities because they promised speedy access back to job centers and schools. But what is often not factored in is that has come at an enormous cost. So there is certainly a benefit in the sense of it has allowed kind of cheaper housing. But when you combine housing and transportation, when you factor in the cost of gas and car insurance and the externalities of greenhouse gas emissions, it actually is not so cheap anymore.

IRA FLATOW: Yeah, and these highways are also pretty expensive to maintain, right?

MEGAN KIMBLE: They’re expensive to build and they’re expensive to maintain. Yeah. I started reporting this book because I learned that the state of Texas had allocated $60 billion– that’s billion with a B– to expand highways in five major Texas cities. It’s an extraordinary amount of money to be spent, as we started talking about not actually solving the problem we set out to solve.

IRA FLATOW: Yeah, and you point out in the early days of thoughts about highway expansion that when it was studied, there were even recommendations that the money would better be spent on public transportation.

MEGAN KIMBLE: Yeah. This is one of my favorite stories that I encountered while reporting my book. So when Eisenhower sold Congress on the interstate highway program, he promised it as one of national defense, so it was going to connect the country in the case of an atomic bomb or nuclear attack, and also build economic prosperity, that we are going to enable trade across this vast nation of ours. So it very much was a program to connect the country.

And what the interstate highway program did is it enabled $25 billion, the largest public works project ever attempted in American history, and the federal government would pay 90% of the cost of construction of these interstate highways. And so the money flowed directly to state departments of transportation, which were called Highway Departments with essentially no oversight by the federal government.

And so what states started doing because they had lots of money flowing into their coffers and people were buying cars in record numbers, is they started building massive highways in the middle of cities. And so they started trying to use that federal money to solve this sort of local problem of urban congestion.

IRA FLATOW: Yeah, that’s not what Eisenhower wanted it for, right?

MEGAN KIMBLE: Yeah, that’s not what Eisenhower intended. And we know that because he appointed this guy, John S Bragdon, as a special assistant to the president to oversee the implementation of the interstate highway program. And Bragdon looked into the matter a few years after the program passed and found that it was running significantly over budget, and it was running over budget because states were using this federal money to build urban highways, which are much more expensive to build than rural ones.

And so he asked Congress, was that your intent of the program, was to solve this problem of local congestion? And he presents his findings to Eisenhower in the spring of 1960. And it’s a really remarkable presentation. I found the actual note cards in the Eisenhower Presidential Library of the text that Bragdon presented to Eisenhower. And in it, he says, practically all the experts on the traffic problem of cities agree that the way to solve urban congestion, rush hour congestion, is through transit. People take up less space than cars. And urban transit is the solution.

But what cities are doing currently is they are using this federal money through the interstate highway program to rip out existing transit systems and build massive highways in their place. And Eisenhower responds, and he agrees. He says those who had implemented the project, the program in this way, had done so against his wishes. He had never intended these massive highways to be built through the center of cities.

IRA FLATOW: And when they started ripping out places to build these highways, the demographics were not quite equal for Black and white, were they?

MEGAN KIMBLE: No. This coincided with the era of urban renewal, in which city planners were looking at, quote, unquote, “blighted neighborhoods” predominantly occupied by Black and Hispanic families, neighborhoods that had been blighted by the same federal government a couple of decades earlier through the practice of redlining. And they saw an opportunity to clear those neighborhoods.

So it’s very clear in the historic record that planners intentionally routed interstate highways through Black and Hispanic neighborhoods and displaced half a million people from their homes along the way. And so it very much had a disproportionate impact on those neighborhoods. And that impact is still being felt today. People who live next to highways suffer higher rates of respiratory diseases. And those are still mostly communities of color.

IRA FLATOW: And as you say, specifically in Texas– and I didn’t know they have the largest highway in the country, 26-lane Katy Freeway in Houston?

MEGAN KIMBLE: Yeah, the Katy Freeway is like the textbook example of induced demand. It’s 26 lanes, including frontage roads. It is this massive highway. And TxDOT expanded it about a decade ago. And within five years, rush hour travel times got worse. And people in Houston drive on that highway. They understand that. I was really struck reporting my book. I went door to door with a lot of activists who were trying to stop a different highway expansion. And people in Houston understand the phenomenon of induced demand. They don’t necessarily call it that. But when you live in a place that is covered by highways and you still sit in crushing traffic, you might wonder, why do we keep doing this?

IRA FLATOW: Yeah. And let’s talk about that. You wrote about the efforts of anti-highway expansion groups in Texas, and there were some successes.

MEGAN KIMBLE: Yeah, so a group in Houston called Stop TxDOT I-45 started going door to door to stop this massive highway expansion. It’s called– locals call it the I-45 expansion, but it actually impacts three interstate highways and will rebuild and reroute the entire downtown loop in Houston, along the way, displacing 1,200 people from their homes, consuming 450 acres of land. And it’s currently an $11 billion project. And a lot of the people who are in the footprint of the expansion didn’t know that their homes would be taken. They didn’t know they had any way to fight back. The authority of eminent domain is absolute. TxDOT can say, hey, we want your home, and all they can do is negotiate on the price.

But this group of just volunteers started going door to door in those neighborhoods impacted by the expansion, saying, hey, do you want this? Hey, do you know that you can say– you know that you can voice your opposition. TxDOT’s own analysis found that the people impacted by this highway expansion were predominantly minority. And so a few of those people filed civil rights complaints, saying this project violates Title VI of the Civil Rights Act because it disproportionately impacts Black and Hispanic people.

And as a result, the federal government actually, under Pete Buttigieg, intervened to pause that project. So they said, hey, TxDOT, we need you to stop work on this project while we investigate these serious civil rights complaints. And those were filed just by normal people, people who I spoke with, who live in the footprint of the expansion, and said, hey, this isn’t fair. This is unjust.

IRA FLATOW: Wow. And this is happening in cities across the country, people fighting back, and cities, some of them, actually taking down their highways.

MEGAN KIMBLE: Yeah. There’s this kind of new resurgence of freeway revolts, which people might remember in the 1960s, there was this massive resistance to highway construction. As these highways came into American cities, tens of thousands of people poured into the streets and said, we don’t want this. And they stopped highways from being built, in Baltimore and Portland and Seattle. Across the country, there were really successful examples of freeway revolts. And there is this sort of burgeoning movement today of this new generation of freeway fighters, many of whom are galvanized by climate, who see the climate impacts of these highway expansions. And they’re really trying to stop highway expansion across the country.

IRA FLATOW: And you’ve mentioned in your book that there are cities that are actually taking down their highways. What cities are those?

MEGAN KIMBLE: Yeah, about 18 cities across North America have either taken down highways or committed to doing so. So one of the ones I profiled in the book is the city of Rochester, New York, which had this inner loop highway circling its downtown, this kind of moat, this sunken highway, that really cut off downtown from the surrounding neighborhoods. And that highway enabled people to actually leave the central business district. And so the downtown had been kind of hollowed out.

And starting about two decades ago, city leaders started talking about, what if we just took that highway away? What if we removed it? And in 2017, the city got a grant from the Obama administration, and they filled in the inner loop highway. They brought it up to grade. And they made a two-lane city street in its place, built this really wide, beautiful sidewalk and bike lane. So there are now apartments built on land that used to be a highway.

Most of those apartments are rented to families earning below the median income, three or four story buildings, and it’s pretty remarkable to go walk. You can see part of the inner loop highway remains. The city of Rochester is in the process of actually filling in the rest of it now. But you can go today and see this sunken highway and then walk two blocks and see a neighborhood, a city. It’s populated. People are walking. They’re riding their bikes. There’s a brewery right there. And it’s really remarkable to see, we can reclaim that space.

I think a lot of people, myself included, I’ve only ever grown up in cities wrapped by highways. It’s very hard to imagine them gone. It’s hard to imagine anything different. But a lot of cities are tearing down highways and building something else in their place. And that can happen over five years. That can happen very quickly.

IRA FLATOW: And Colorado is actually taking a different approach, right? What are they doing?

MEGAN KIMBLE: Yeah, so that really shows how this is a climate story. So Coloradans elected a Governor Jared Polis, who made climate a top priority of his administration, and the legislature, passed a bill requiring all state agencies to make a plan to reduce greenhouse gas emissions by 90% by 2050. And so the Colorado DOT looked at its portfolio of projects, which included widening I-25 through the heart of Denver, and said, hey, we can’t actually widen this highway and meet our greenhouse gas targets.

And so they took that widening off the books. They said, we’re not going to do this, and we’re going to allocate that money to something else. And that something else is bus rapid transit. So basically, we’re going to help build a more robust transit system in Denver so that people can ride the bus, which lowers greenhouse gas emissions, and get people where they’re going without a car. And that is a really remarkable example of climate policy dictating transportation funding.

IRA FLATOW: Very interesting. You’ve been reporting on this issue for a long time. You’ve written the book City Limits. What’s your biggest takeaway on this topic after all of these years?

MEGAN KIMBLE: Yeah. I started reporting the book with kind of the same question that you have in this program, which is, if widening highways doesn’t work to fix traffic, why are we still spending billions of dollars to widen highways? And the answer I have come to after four years of reporting is that there is this persistent belief in the US that cars help create prosperity, that cars enable economic development, and that without a car, our economy will collapse.

And so many other countries disprove that. Lots of cities in the US disprove that. There’s so many different ways to tilt at that narrative. But that is this persistent belief from politicians of both parties, that cars create prosperity. And until we counter that, we’re going to keep making the same mistakes.

IRA FLATOW: Do you think that might be changing? Are people thinking differently, starting to look at highways in their neighborhoods in a different way?

MEGAN KIMBLE: Yeah, absolutely. I mean, like I said, it’s definitely becoming a climate fight. People are realizing that widening highways is only increasing our emissions, but I think it’s also becoming a quality of life fight. Young people don’t want to drive. They want to live in places that are walkable. They want to not spend the money on cars. A car is often the largest share of a household’s disposable income after housing. And so people don’t want to spend the money, and they don’t want to spend the time driving. So I think there is a real shift, particularly as younger generations move into the housing market. They don’t want to just live in the suburbs and drive everywhere they have to go.

IRA FLATOW: Yeah, this is a fascinating book, Megan. As someone who loves to read about highways and traffic and stuff, you’ve done a wonderful job here explaining the whole thing to us, especially the history of it, which is fascinating itself. Thank you very much for taking the time to be with us today.

MEGAN KIMBLE: Oh, thank you, Ira. Thanks for having me.

IRA FLATOW: Megan Kimble, journalist and author of the book City Limits, Infrastructure Inequality and the Future of America’s Highways. And you can read an excerpt from that book on our website, sciencefriday.com/highways.

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