Greg Shill on the Past, Present, and Future of Transportation.

A law professor by day and also by night, Greg Shill has thoughts on what we've gotten wrong, how we got where we are, and what we can do in the next decade to ensure a better transportation system.

If you read the Atlantic and you have even a slight interest in transportation, you may have come across Greg Shill’s piece “Americans Shouldn’t Have to Drive, but the Law Insists on It,” published in July 2019, when commuting was still a thing. Or, if you’re like me, and have a professional SSRN account, you may have seen his scholarship, and especially the inspiration for the Atlantic piece, “Should Law Subsidize Driving?” The answer, as you might deduce, is no.

Greg has built an impressive Twitter following in the last two years. He’s a law professor with over 5,000 users subscribed to read “aggressively medium” takes on how the United States’ byzantine legal system has caused Americans to drive more and more over the last few decades. Professor Shill isn’t the only advocate for legal reform, but he’s certainly become one of urbanist Twitter’s most fun follows to learn more about transportation law. That’s what you’re here for, anyway.

Greg and I talked transportation, but we also talked zoning reform. The two are woven together and their confluence has fueled a national, disastrous land use crisis that’s forced Americans into their cars and off their sidewalks, bus lanes, and, where existing, bike lanes. Driving should be a choice, not a consequence.

Below, find our conversation, lightly edited for clarity.


Sam Sklar  

I'm here with Greg Shill. Can you tell us who you are and what you mainly do?

Greg Shill  

I'm a professor at the University of Iowa College of Law. I'm also an affiliated faculty member at the National Advanced Driving Simulator at the University of Iowa College of Engineering

And I wrote an article that was published a few months ago in May 2020 in the NYU Law Review, titled “Should Law Subsidize Driving?” and a short-form summary of it for the Atlantic called, “Americans Shouldn’t Have To Drive, But The Law Insists On It.”

[Ed. Greg published a new article after this interview was conducted, also in the Atlantic: “The ‘Trump Train’ Drivers Had Reason to Expect Impunity.”]

Sam Sklar  

We've done a lot of good things for transportation in the past: a growing number of options for people. From the legal perspective, but obviously, feel free to talk about whichever perspective you'd like, where do you think we've gone off the rails in terms of transportation planning?

Greg Shill  

I think the question of what's law and what's policy is an evergreen one. And so, as you mentioned, my lens is legal. To some extent, I think law is driving some bad decision making. But I think to a much larger extent, laws are entrenching bad decisions that often had been made by people long dead, which would be difficult to find public support for today. [It’s] what we would call a “dead hand effect” from law. 

I think we've made a lot of mistakes. I think it's important to talk about the context in which those mistakes were made, as well as the substance of the mistakes, in order to understand how they were made, and what might work in terms of reform. One thing that comes up a lot is the choice, by a mix of political elites at the local, state, and federal level on the one hand, and commercial interests aligned with the auto industry on the other, to remake the city into a destination for suburbanites and for offices as opposed to a whole unto itself. 

And that process really began in the late 19th century, and continued long after long after it had already done most of its work, which is long after the suburbanization of the American city was largely complete by the 1970s, and a decade or two later in the Midwest. That's a story about elites driving decision making [Ed. Robert Moses, anyone?]. It's also a story of local officials reaching out for assistance to do things that were actually bad for their own cities. To some extent, this is a top down process from Washington and from states. But the reason the Interstate Highway System ran so deeply into cities was mainly because (here I'm not a historian, so I don't want to make the claim too strongly) local interests and local officials brought the highway into the city, as opposed to it being directed into the city. The original plan did not call for the  urban freeways that we have now. I think that's important. 

If this photo looks appealing to you, you may be suffering from suburbia. Ask yourself: how do I walk from my house to my neighbors’? Image: Wikimedia Commons\David Shankman

Zoning was a big innovation in land use regulation in the early 20th century. There are different kinds of zoning, just like you might see different other kinds of technologies: Betamax and VHS come out and they compete, and iPhone and Androids come out and they compete, and in some places one [choice] sticks more than the other. So there was what was called “racial zoning,” and its purpose was explicitly racist. (It gets invalidated in Buchanan v. Warley). And then, about a decade later, we have Euclid v. Ambler, which is the Supreme Court case that validates zoning, and zoning in that case is not explicitly racist;  It is based on use, and it's also based, to an extent, on class. And so that becomes the model that's copied around the country. 

It's increasingly acknowledged today, that zoning has racial/segregation consequences. And I don't think that that's accidental, I think in many cases, it's on purpose. But it’s not inherently racist to say that you want to live in a neighborhood that is quiet, for example, right? If you increase lot sizes, and prohibit multiple dwellings from being constructed on a single parcel, you're going to ensure that your neighborhood is a lot quieter than if it allows greater density. I think people who, like me, are eager for reform of zoning and transportation, the connection here, just to make it explicit, is that you can't really get around by any other mechanism other than a car, if you[r neighborhood has] very low density. And most of our suburban zoning, and even some of our big cities, [like] San Francisco, most of the residential real estate is zoned for single family housing, which starts a doom loop of: you need a car to get around, you have car, and now you're bought into a car based system. So paradigm shift becomes very, very difficult. 

I'm not making a defense, at all, of single family zoning, what I am doing is saying, “I think we should be mindful of the variety of motivations here.” And that matters, because where you want to most radically change zoning is something that ought to be driven by where it makes sense logically, for more density to be to go right near transit in a city, and so on. And that's also where I think you can make the strongest political argument.

Sam Sklar  

So to summarize, where you think we've gone off the rails here is we haven't moved quickly enough to reform zoning in the US? Is that what I'm hearing or that we're forcing people into a car-based system based on the law and the policies that sprung from them. Did I catch it right?

Greg Shill  

There's a lot going on, but there's a handful of extremely important sources of regulation that de facto compel reliance on the automobile, and one of them is zoning. Another is the wildly disproportionate funding that highways and roads receive relative to public transit. We can get into the weeds on parking requirements and regulation of vehicle safety and so forth. You can add a bike lane—even a really nice bike lane—in a low density suburb and the impact on actual transportation behavior is going to be very low. 

We have locked in the law and that makes paradigm shifts very difficult. If you put up a four-story apartment building and a bike lane in a suburban neighborhood that's otherwise filled with cul-de-sacs and cars going 50 miles-an-hour on arterials, neighbors aren’t crazy to think that's just going to bring a lot more traffic because the 50 people that live in this apartment building are going to have to own cars, and they're going have to drive everywhere. 

The zoning map from Johnson County for Iowa City, where the University of Iowa is located. It’s a rainbow of a map, painstakingly authorizing uses for every parcel in the city. That pale yellow color is zoned for single-family residences, even so close to downtown.

So it's important to think systematically about changing the paradigm, as opposed to trying to do all à la carte changes and laws that would make [systemic change] somewhat difficult. Zoning acts as a prohibition on change, and even if you get a variance for one project, by definition it’s not systemic; it’s not a paradigm shift; it's a surgical change.

Sam Sklar  

So along those lines, let's move on to the next question about what we can do within the system that we have today to help effectuate change: to bring more equity and bring more access to opportunity for folks across the country, no matter their financial status, or their ability to pay to use a system. What do you think we can do either from a law perspective or from a policy perspective to help move that change along?

Greg Shill  

The first thing I'll say is that, by and large, the most economic opportunity in this century is concentrated in cities. And that's a continuation of a trend from the 19th century. It's just intensified quite significantly in the past quarter-century in the US (and overseas as well). 

One way to frame the question is, “How do we make it easier for people to live in cities, and for places that are city-adjacent to become a bigger part of the solution?” There are a lot of micro changes that are necessary. That's what lawyers love: getting into the weeds...but that's probably a different conversation. 

I think the political conversation should focus on what is the appropriate level of decision making. Take this cul-de-sac suburb: you're not going to persuade neighbors that they're going to benefit from an apartment building, replacing a single family home in their cul-de-sac. Why? Because they won't. And giving neighbors a veto is a recipe for failure. At the same time, those neighbors may want their municipality or their area to produce more housing. Because they recognize that there's an affordability problem, that [a lack of new housing] is hindering their economic growth if they can't grow the population, and that rents and mortgage payments are eating up a growing percentage of their income It's in their interest, just not in their backyard, and there's a logic that’s not merely: BANANA (Build Absolutely Nothing Anywhere Near Anything). Some people have that view, but really, most people don't. 

I hope you’re reading this piece, or this picture makes no sense.

Where do you do the growth politics? I don't think you can do it at a neighborhood level. Now, in this country, especially in the Northeast, municipalities, townships, villages, etc., are so political and communities self select to such a degree, that it may not always be possible to do the change at the municipal level. You might have to go to the state level, or to the county, or so on. That's one reason we see some of the more promising efforts at reform coming at the state level in Oregon and in California. It's hard to make the case at the state level, that there ought not to be more housing. So that's important. 

The other piece though that I think has been neglected is the federal role. And I think I can theorize about why people have overlooked it. One intuition is that the federal government doesn't dictate zoning policy. Fine. You see the weaponization of zoning and land use politics — NIMBYism by the Trump campaign this [election] cycle. I don't want to draw too many conclusions from that. What I would say is, to the extent that urbanists have been thinking, let's not federalize this question, or let's not nationalize the question, because then we'll have a left/right, divide, and we'll never, we'll never bridge [that gap]. The horse is out of the barn. 

Probably the right vehicle to look to is highway funding, because the federal government spends close to 50 billion a year on highways. If states, it's [doled out], almost exclusively through block grants to the states, and if states lost even a share of their allocation, they would have to rethink a lot of things. When drunk driving was getting taken more seriously, the federal government attached strings to a small percentage of highway funding that said that states have to raise their drinking age. It was upheld by the Supreme Court, because it was closely enough related to compelling federal interest. 

Anyone who plays Geoguessr should be able to tell me where this HOV lane is.

The use of highways is a lot more efficient if the lanes are managed efficiently, with HOV lanes and bus lanes, and if the land use near them is managed more efficiently. If you have tons and tons of sprawl, that generates a lot more congestion, because everybody has to drive and drive further away than would otherwise be the case. 

So I think it would be entirely appropriate, for example, to condition 5% of Federal Highway funding on the accomplishment of certain transportation related policies.

Sam Sklar  

Do you worry that going down that road would open a slippery slope where anytime DOT wants to do something, they'll attach a little 2% funding rider to the reauthorization bill, or will say we want to compel you to do X, Y, and Z. So we're going to make it contingent on you doing X, Y, and Z, or we're going to withhold some funding.

Greg Shill  

Many people don't know that DOT already does that. There are all sorts of programs for which the federal funding is partly contingent on state or local compliance. I'll give an example. There are all these uniform manuals that the states have to adopt in a substantially similar form. The two that come to mind are the manual of uniform traffic control devices (MUTCD) and the Model Minimum Uniform Crash Criteria (MMUCC).

There are funding streams that are attached to substantial compliance with these documents. Substantial compliance does not mean rote adoption, so there is some room for variation, but that's one example. 

Photograph by Getty Images, illustration by Emily Judem/WGBH News via GBH News.

The Department of Energy conditions some funds on states adopting a right turn on red [mandate]. There is a safety exception, but only a tiny number of jurisdictions take advantage of it. And interestingly that rule was promulgated, apparently without reference to the safety implications. Recently, the Institute for Transportation Engineers (ITE) actually withdrew its guidance in favor of the right turn on red. It had previously I think in 1986 or so, favored right turn on red as an efficient way to move traffic and save people idling. But they rescinded that guidance in light of evidence that it's harmful to people outside the vehicle. So, no, the DOT and the US government in general are already in the business of attaching strings to funding. This would be a very modest extension of that in accomplishment of or in the pursuit of already popular goals: public safety, emissions reduction, congestion reduction, and saving money.

Sam Sklar  

Do you think that it will be more effective going forward to offer states or the recipients of federal monies, carrots or sticks in that regard, because we just talked about whether the money is a bonus for hitting certain goals or a punishment for not meeting goals? Which do you think would be more effective to help guide states and localities into adopting more meaningful reform?

Greg Shill  

The problem is, every year, the federal government makes a giant carrot cake, and ships it off to states. So that's the 48 billion or so in highway funding. If they want change, and not more of the same, I don't think it's all that useful to say, “Here's a single baby carrot. If you take this carrot cake, and you do things that we like with it, you'll also get the baby carrot.” 

In the Obama administration, there were programs like that. I think that's how we get things like three-foot bike lanes on arterials, where the speed limit is 40, and everybody's going 50. It's a cosmetic change that doesn't do anything to move the paradigm. 

This is the issue with paradigm shifts, right? In general, when you're campaigning, you want to reform. So maybe your proposed reform is a mandatory seatbelt law. You make the case for mandatory seatbelt law: it's scientifically grounded in safety and so on. And maybe you get a personal liberty objection, so you settle on a compromise that only occupants in the front seat have to wear them. Okay, that's obviously not as good, especially since children tend to sit in the backseat and we’re especially worried about children. But it is pretty good. And most of the time, cars are occupied by one person, who obviously is the driver. 

So if you actually got that compromise, it would go a long way to improving safety. That's not a paradigm shift. That's where incremental change can help. If you're talking about making it safe for people to bike in a suburb, or making it possible to build cost efficiently in a city, it’s not enough to fund one project, or to allow one bike lane to get built—a bike lane to nowhere, a bike lane that's swamped by traffic conditions, or not connected to a network. 

When one has a goal, obviously, one wants everything that is necessary for that goal, right? The question is just what is necessary for the goal. And if you're talking about seatbelts, or many other types of reforms, incrementalism, and partial solutions are in fact, partial solutions. They are slices of bread. Not as good as the whole loaf, but division makes sense and individual slices are meaningful. Networks and paradigms, by contrast, are harder to disaggregate without doing damage to the whole. They are closer to lumps.

Sam Sklar  

Along those lines, I'm very interested in the legal ramifications of a lot of the policies that have come out, especially during the Obama administration. I'm curious to see if you could walk us through an example of a decision or something in the code that compels politicians make these bad decisions. Is there something that could be stricken from the record or does there need to be some sort of challenge in court to make it easier for state DOTs to build Complete Streets across a network? Does that make sense?

Greg Shill  

It makes sense but I would reframe the question a little bit. The short answer is state DOTs have authority they need. They are not obligated to add lanes, for example, or raise [speed] limits and so on. The notion that the MUTCD compels [state DOTs] is false. They may hide behind the MUTCD or  they may hide behind level of service. It's a political decision that's been technocratized in order to insulate itself, and, it’s a political problem, not a legal one. 

The reframing that I would suggest is that transportation funding is done in multi-year cycles, and that is unique among most federal appropriations. You can see why, right? It takes a long time to build a project. And so you don't want to have political disputes pulled up if you're building a bridge, and it has 10 components, but building nine, [makes it] useless, right? The bridge only has value once you've built the 10th component. Building a bridge is ‘lumpy’—parts do not have value until the whole is complete—so it makes sense to have a lumpy appropriation that's multi-year. It makes sense technocratically.

This bridge is actually called The Bridge to Nowhere. It’s in Mount Baldy, CA, and is simply a tourist site now. There are metaphors abound as to the decisions that went into building this bridge. Image: Wikimedia Commons\Jason Hickey

It also makes sense politically, but for bad reasons: it superficially depoliticizes the issue of transportation over the five (or whatever) year period of the transportation bill after it's been funded. Politicians can go to ribbon-cuttings and hold press conferences and brag about all this money coming to their district. It's classic pork; and they get the pork without doing the politics. From their perspective, you can see why they're comfortable with the status quo, whatever their vision of the world, right? Just from a “get reelected standpoint”. You get to go out there with a shovel every so often and put on a hard hat for the photo.

I don't I don't know what to change about that. I mean, I don't know that you want to fight about it every year. I do think we need to raise the salience of transportation as a question, because of the postwar consensus of highways, highways, highways. I think we've gone past the limit of utility on that.

Sam Sklar  

It's definitely tricky. And it's not going to be changed, certainly for this reauthorization, which is supposed to happen in the next month or so. We'll see if we get a continuing resolution or an actual omnibus bill here. 

My last question here is about the future. And this is, if you felt the last two are open ended, and you might need to reframe, let's talk about this one. I'm just curious about what you think a successful 2030 transportation paradigm looks like. 

So I've had people reframe this to 2022, just to be a little bit more realistic. But if we're going to look further out—10 years from now—what are some of the outcomes of a successful decade here on transportation policy?

Greg Shill  

It’s a big question. A decade is a short time and if you're thinking nationally, it's probably a lot of time if you're thinking what changes can be visible in cities. So maybe I'll break it up a little bit if that's okay.

The first thing I'll say is that a successful transportation paradigm is one that you don't think about, right? What is a successful Internet? One that works. Nobody cares about the Internet qua the Internet. And transportation is a derived demand. Overwhelmingly, people use transportation in order to get from point A to point B, and the less they have to think about that, the less to pay for, the less risk they create for themselves and others to damage the climate and so on, and the process, the better. 

And so a “transportation paradigm” that's better than what we have today is a better world, because that would be the returns on a better transportation paradigm—a fairer one, a safer one, and a greener one. 

In terms of the next decade, to be a bit of a Debbie Downer, I think we have to acknowledge that we're already locked in for the next decade in the most optimistic scenarios.

For the last few years, sales of trucks and SUVs have been the largest share of US auto sales. These vehicles are disproportionately large, heavy, tall, and dangerous to people outside the vehicles, more so than any prior generation of vehicles. These have nothing to do with your grandpa's pickup truck on the farm. It's almost a misnomer to compare them to old generations’ [trucks]. I grew up in southeastern Michigan. I get a little frustrated when people equate these things that have the same name, but are really different. 

We have a vehicle fleet that is very heavy, fast and tall. And there are studies going back quite some time that show the dangers of those physical characteristics for people outside the vehicle, including other vehicles, let alone people walking, biking or using wheelchairs. We've locked that in. We also have massive distraction by drivers, often worse today, in these vehicles because they tend to have very large touchscreens. And there's a growing literature on that. So we have to think about what we can do within those constraints. 

There’s also political impossibility of raising the gas tax to such a level that it would actually have more than a marginal impact on behavior. It hasn't been raised federally in 27 years. It's difficult to envision a politics where it can be raised to a carbon-pricing level, where it really forces internalization of costs, as opposed to just raising some revenue for roads. That's the box that we're in. 

This is the most succinct chart that relays the importance of federal gas tax reform.

I think if you're talking about changing the national landscape, in that box of a decade, it's really hard. The good news is a lot of people already live in areas that have a land use pattern that would allow smaller changes to have a big effect. So you have a lever function of changes that are done locally. What am I talking about? Making it easier to build homes so that people can live closer to where they work, but also, 80% of trips are not work trips, so not just closer to where they work, but also closer to the grocery store, their kids’ school, the dry cleaner, whatever. So that's on the housing production and regulatory liberalization to build homes. 

The other thing that can be done quickly is enhancing bus and bike infrastructure. We have a costs problem in US infrastructure and it is multifaceted. It runs to every type of infrastructure: bike lanes, subway lines, underground freeway tunnels, you name it. Solving that is going to be a major challenge, and it won't be done in the timeframe you're suggesting so I think tethering the success of transportation reform to cost reform is risky. The good news is that a lot of the changes that we need are actually cheap. 

Alon Levy’s blog “Pedestrian Observations” has an in-depth analysis to the issue of skyrocketing costs relative to marginal returns. It’s well-worth a follow for other reasons, too.

So: creating bus lanes. Now, in our high cost paradigm, the bus lane is actually more expensive than you would think. It might cost several hundred thousand dollars to build a bus lane of a relatively short distance but in terms of money saved, direct expenditure saved on road repair, and cleanup from crashes and so on, as well as the social benefit of a reduction in emissions congestion and making it so that people can just take the bus. The bus can be competitive with private [transportation]. I think that would go a long way, bus lanes and bike lanes that are a network and that are protected. 

There are dozens if not hundreds of [places] around the country that are patting themselves on the back after striping bike lanes with no protection, and they are kidding themselves. And I think they're going to look incredibly foolish creating these Maginot lines of protection that they would never send their kids in. On a more positive note, these interventions—more homebuilding in cities, and better bus lanes and bike lanes—can create a positive feedback loop. So more people take the bus, and then there's a better case for adding more buses, and so on. And the same for bike infrastructure. That stuff is all within the domain of cities themselves. 

We talked earlier about nudges, right? And what state capitals and the federal government can do. I think that that's really important. But if you're a mayor, and you want to do this, find a way to build a coalition and get it done, because you have the power to do it. And that's not true for so many problems, right? If you're the mayor, and you know that a lot of your constituents don't have health care, or their public schools aren't getting enough money, there's so many hard constraints that prevent you from meaningfully mediating those problems. 

That's just not true in housing and transportation. In fact, you can increase the revenue that your jurisdiction receives by permitting more housing. And you can increase the spending power of your constituents by allowing them to take public transit, rather than spend an average of $9,000 a year operating a car, that they can turn that money around. And yes, some of that they'll spend on Amazon or whatever, but a lot of it will be spent locally. Mayors and other local governments should have a growth mindset to use the tools that they have, which are considerable.

Sam Sklar  

So I'm hearing a hope and doom in the same sentence here. And that's an interesting concept to rationalize together. You know, the example that I like to give is when we look at a picture of modern Amsterdam, central Amsterdam, and we see this bike haven paradise, we really need to look back at the 1970s, where it looked like the downtown of a lot of US cities, which was filled with cars. And so among the legal avenues and the political avenues, I think it's a cultural attitudes as well, that we have to fight for we have these local bike coalitions and nonprofit organizations and advocacy groups that are going to make a huge difference if we can really band together and figure out how to get everyone to work toward a similar goal.

Greg Shill  

I think your last point is really important. And there's more activism on this than there has been a long time. I think things are complicated right now with the pandemic, and here I'm sort of stepping out of the role of law professor into an area where I have less expertise. With that being said, there seems to be a lot more online activism than in-person activism. And I think that was true pre-pandemic. 

There's no substitute for talking to your neighbors, persuading them to build coalitions with local groups, groups on which you don't agree on everything. To get things done, doing the bread and butter work of local political organizing, to translate your good ideas into policy. 5th Square in Philadelphia, Greater Greater Washington in DC, the California YIMBY groups (there’s lots of them)—as you mentioned—there are a lot of groups doing versions of this around the country. 5th Square in Philadelphia has built a truly impressive organization: a lot of things in the database, a lot of supporters, well-attended meetings of coalitions, and they've had a real impact in Philly. And I think there are probably other examples out there. But that's what's needed to support the politicians who are sympathetic, but are worried about backlash, because we know the backlash is coming. And also to change hearts and minds for, you know, for folks that this issue is not salient to them yet or that they have a different view.


If you’d like to learn more about Professor Shill’s work, he’s been quite busy in the last few months. He spearheaded an online symposium called “The Future of Law & Transportation,” which dovetails nicely with this blog. You can watch the videos from the event here.

He’s also started a podcast, with an economist, called “Densely Speaking: Conversations About Cities, Economics & Law.”