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Episode Summary: Do people drive less because they live in buildings that don’t provide parking, or do they live in buildings that don’t provide parking because they drive less? That question has huge implications for how we build and rebuild our cities, yet researchers have struggled for decades to answer it conclusively. UCLA professor Adam Millard-Ball joins us to discuss new research that finally — we hope — puts the question to bed. Taking advantage of San Francisco’s affordable housing lottery, Millard-Ball and colleagues find that (as-good-as-)randomly assigning tenants to different buildings and neighborhoods has substantial impacts on their transportation choices, with lower parking ratios resulting in less driving and more transit use. We talk about what this means for housing and parking policy, and what it says about the behavioral shifts needed to make cities more affordable, accessible, and sustainable.

  • “A voluminous international literature in urban planning and economics considers how neighbourhood attributes such as public transportation access, residential density and walkability relate to automobile ownership, vehicle miles travelled and emissions (e.g. Ewing and Cervero, 2010; Giuliano and Narayan, 2003; Salon et al., 2012; Stevens, 2017; Zegras, 2010). To a lesser extent, researchers have also investigated how the accessibility of job opportunities correlates with employment and household income (Marinescu and Rathelot, 2018; Sanchez, 1999) … A significant challenge for understanding how location-based amenities such as public transportation affect residents’ travel behaviour and employment opportunities, however, is that people choose where to live, and they do so based in part on local factors such as the availability of parking and public transportation. This self-selection into residential (and workplace) locations means that the vast majority of inferences from the transportation–land use literature are susceptible to selection bias (Van Wee, 2009).”

 

  • “As in nearly all areas of social science research, randomised experiments are the gold standard by which to identify causal effects. In principle, researchers could randomly assign households to different types of neighbourhoods and then observe their behaviour, but this is rarely practical or ethical (Cao et al., 2009) … In this article, we leverage the housing lottery programmes in San Francisco to overcome the aforementioned research limitations and provide causal interpretations of the impacts of specific neighbourhood characteristics and parking provision on households’ transportation behaviour and economic outcomes.”

 

  • “In San Francisco, nearly all new housing developments with 10 or more residential units must offer a government-specified share of ‘inclusionary’ units at below-market-rate (BMR) prices, either directly on site, directly off site, or indirectly off site by paying a fee. As might be expected, demand for new BMR units substantially exceeds the available supply – one recent lottery for 95 rental units attracted 6580 household applicants (Badger, 2018). Because of the very low odds of winning, eligible households generally apply indiscriminately to many different housing lotteries. Those that are fortunate to eventually win a BMR unit are thus effectively assigned to live in specific buildings and neighbourhoods. In essence, San Francisco’s housing lotteries provide as-good-as-random assignment of people into homes.”

 

  • “To validate our assumption that housing assignments are as good as random, we use a data set of all 107,310 applications to 59 BMR housing lotteries held between July 2015 and June 2018, which we call our applicant sample … Our primary data survey sample consists of all BMR units for which we have occupancy and parking data, and comprises 2654 units in 197 projects that were occupied as of April 2019. Almost all (2605) of these units were built under the Inclusionary Housing programme.”

 

  • “Our analyses consider how four primary measures of transportation accessibility affect household behaviour. We quantify private automobile accessibility using each building’s ratio of parking spaces per residential unit. We use the Center for Neighborhood Technology’s AllTransit performance score to measure public transport frequency and quality, and we use the WalkScore company’s Walk Score and Bike Score metrics to measure accessibility by walking and cycling, respectively.”

 

  • “We begin our empirical analysis by demonstrating that assignment of lottery-winning households to housing units is as-good-as-random, which facilitates causal inference. To do so, we examine the patterns of lottery participation and repeat-entrant behaviour among households in our applicant sample. While each lottery is itself random by design, households might possibly choose to selectively enter only certain lotteries, for example by forgoing the chance to rent or buy in a building without parking or in one that is distant from a public transport stop … A reasonable hypothesis is that households are not selective, given the low probability of winning any lottery … We confirm our hypothesis that households are not selective using regression analysis. Specifically, we estimate whether a household is more (or less) likely to participate in a particular housing lottery depending on how the characteristics of that lottery differ from those of the first lottery that the same household entered … We find no evidence that households skip lotteries based on project or neighbourhood characteristics such as parking and public transport accessibility.”

 

  • “Having demonstrated as-good-as-random assignment of people into homes, the remainder of our analysis focuses on the household survey that we fielded. We begin by examining the relationship between household car ownership and a building’s parking provision and neighbourhood transportation accessibility. Figure 3 demonstrates a clear and substantive trend: the more parking in a building, the more likely a resident household is to own a car. In buildings with no on-site parking, only 38% of households own a car. In buildings with at least one parking space per unit, more than 81% of households own automobiles. Moreover, for buildings with intermediate amounts of parking, the pattern in Figure 3 shows monotonically increasing car ownership rates.”

 

  • “A similar relationship between parking provision and car ownership is shown by the regression models in Table 3. In Column (1), a minimal univariate linear specification indicates that a one standard deviation increase in a building’s parking ratio – about 0.43 additional spaces per unit – causes a household to be 14 percentage points more likely to own a car.8 As discussed above, parking ratios are correlated with the other neighbourhood-level factors such as public transport accessibility and walkability. However, Columns (2) to (4) show very similar estimates (12 percentage points) using specifications that also include regressors for accessibility by public transport, walking and bicycling, along with survey respondent-level controls.”

 

  • “In addition to impacting car ownership, parking ratios and transportation accessibility also affect household transportation mode decisions. Figure 4 shows the raw correlations between project- and neighbourhood-level transportation availability characteristics (columns) and surveyed households’ travel behaviour (rows). As expected, the frequency of driving (bottom row) increases with the building’s parking ratio and decreases with neighbourhood public transport, walking and cycling accessibility. The frequency of bicycling, walking and public transport use (the top three rows) show the opposite relationship to that for driving. Across the board, these correlations strongly support the conclusion that households choose between driving and other modes of travel based on the quality and availability of modes of transportation.”

 

  • “To more formally estimate the importance of these transportation availability measures in shaping households’ choices, we present multivariate regression analysis in Table 4. In Panel [A], the dependent variables are a respondent’s self-reported frequency of travel by single-occupant vehicle, public transportation, walking and bicycle, respectively … As expected, increasing accessibility by public transport, walking or bicycling increases the frequency of use of the corresponding mode, even after controlling for respondents’ household characteristics, as well as for the building’s parking ratio. Nearly all of the estimates are statistically significant at the 5% level (the p-value for public transport score in Column (2) is 0.055), and most magnitudes are nontrivial.”

 

  • “The impact of parking and transportation accessibility on commute mode choice appears to be more muted than for non-work trips. This might be because commute trips are relatively more constrained, for example by workplace parking options or public transport proximity, whereas non-commuting trips entail more choice of potential destinations for (say) shopping or recreation.”

 

  • “Finally, we evaluate employment outcomes and focus on two key transportation factors that the literature suggests may affect labour market opportunities, particularly for low-income workers …For our surveyed households, who are essentially randomly assigned to a residential location, Table 5 suggests that neither public transport accessibility nor parking ratios have any impact on the probability of a respondent being employed full time (Column (1)). There is a similar null relationship with other labour market outcomes in Columns (2) to (4). One possibility is that these estimates are only indicative of the strong economy and minimal unemployment in San Francisco at the time of our survey in 2019. An alternative explanation is that small changes in car ownership and public transport access have little relevance for employment prospects after residential self-selection is fully accounted for via as-good-as randomisation. For example, residing in a low-accessibility neighbourhood might be correlated more generally with being unemployed because of some third factor such as discrimination in both housing and employment markets.”

Shane Phillips 0:04
Hello, this is the UCLA Housing Voice podcast, and I'm your host Shane Phillips. Each episode, we discuss a different housing research paper with its author to help our listeners better understand how to build more affordable and equitable cities. Our guest this time is Professor Adam Millard ball of UCLA, and my co-host is Mike Manville. Today we're talking about how the built environment and especially parking affects the transportation choices that people make. While that might sound like more of a transportation question than a housing one, it's housing and land use policy that determines how much parking gets built in pretty much every city in North America. We've known for a long, long time, that things like limited parking availability, and high quality transit service are associated with less driving, and more transit use. But it's been surprisingly difficult to establish a clear causal connection between these things. Does someone drive less than the average person because they live in a building with limited parking? Or do they live in a building with limited parking because they drive less than average? The answer to that question has a bunch of important implications for our transition to more affordable, accessible and sustainable cities, taking advantage of San Francisco's affordable housing lottery program, and some variation in neighborhood transit quality and parking within each building. Adam and his co-authors have a firm answer to that question. They've achieved something that researchers have been trying to do for decades, and so we're really excited to have him on to discuss their work. The Housing Voice podcast is a production of the UCLA Lewis Center for Regional Policy Studies. And for the past few episodes, including this one, we've received production support from Olivia Urena, a grad student in the Master of Urban and Regional Planning Program here at the Luskin School of Public Affairs. Thank you so much, Olivia, we really appreciate your help. If you want to help the show, you can give us a five star rating and a review. And if you have any feedback or ideas for the show, you can email me at Shanephillips@ucla.edu. Let's get to our conversation with Professor Adam Millard-Ball.

Our guest this week is Adam Millard-Ball, Associate Professor of urban planning at UCLA. Adam joined our faculty, I think about a year ago and we're really excited to finally have him on the podcast. So welcome to the show, Adam and a belated public welcome to UCLA.

Adam Millard-Ball 2:32
Thank you. It's really nice to be here. And this is my first ever podcast. So let's do it.

Shane Phillips 2:38
Yes. Mike Manville is our co host today. And so welcome, Mike.

Michael Manville 2:44
I'm glad to be here co hosting, and I, like you, I'm thrilled to welcome Adam to the podcast. He is a top-notch transportation researcher, top-notch environmental impact researcher. So UCLA is lucky to have him and the podcast is lucky to have him.

Shane Phillips 3:01
We're gonna open the podcast how we always do with a question about kind of where you're from somewhere you love. I think you said you're going to do San Francisco, if we were visiting where you would take where would you take us I think we've all been there before. But maybe you have a special insight having lived there.

Adam Millard-Ball 3:16
Sure. So I grew up in England as might be obvious from my voice. And joining any university in the middle of a pandemic isn't the best recipe for getting to know a new city very quickly. So I'll say a few words about San Francisco, which is probably the place I've lived longest in the in the US. And it was actually the first place say I lived in California when I moved to the US. And at that time, there's this big freeway that loomed over Market Street, Central freeway. It had been closed since the earthquake but we're still up there. And if we are taking your tour, I'd like to show you that neighborhood. And really what an amazing difference it makes to remove that freeway, not just in terms of it coming down. But also in terms of what the city did with that right of way. Because I think the temptation for some, like former road rights of way or former freeways is to say let's make it a park. Let's make it something that's going to offend as few people as possible. But in San Francisco, it was remarkable how much they turned over those former freeway parcels into housing, and half of them into affordable or supportive housing, and even the interim uses, there was a farm there for a while, it was truly an urban farm as an interim use until the housing came online. And we'll talk about parking I'm sure in quite a bit, and that is also one of the first places that San Francisco pioneered in removing parking requirements and introducing parking maximums.

Shane Phillips 4:54
Yeah, I think I've actually visited that on a tour during some conference I was at in San Francisco. So your article was published last year in Urban Studies, along with your co-authors, Jeremy West, Nazneen Rezaei and Garima Desai. And it's titled 'What do residential lotteries show us about transportation choices', I will admit to a little trepidation about discussing this paper, not because it isn't great, because it really is. But because the findings are so straightforward, and we have 45 to 60 minutes to fill. But to set this up a little bit, for a long time, researchers and practitioners have assumed I think, understandably, that the environment people live in shapes the choices that they make about how to get around. But it was really, really difficult to be sure or to know the size of that effect. Because we know that people choose where they live based on their preferences. So on the one hand, maybe people drive less because they live in apartments that don't provide on site parking. And on the other hand, maybe they live in apartments that don't provide parking, because they drive less. The same goes for access to public transit, and walking and biking. That's a selection bias problem that looms really large in this type of research. But in this paper, you found a really clever way to bypass it, and to isolate the impact of the built environment itself. And in doing that, you've developed some very strong evidence that less parking and better transit really do cause people to drive less, regardless of their personal preferences. So that's my very quick summary of what you found and why it's important. But now let's just take a step back. And I'd like to have you set this up for us. There's a ton of research examining the relationship between the built environment and people's transportation choices. What did we know going into this study? And what did we merely think was true, but couldn't really be sure of

Adam Millard-Ball 6:54
So something we know a lot about, before the study and after the study, and there's literally 1000s of studies, perhaps even tens of 1000s of studies on the link between the built environment. So how walkable neighborhood how much transit, how dense, what's the mix of uses, and how people get around. And so there's pretty consistent findings that emerged from that research. That yeah, in dense mixed use, walkable places people drive less, when transit is better, people drive less. In walkable neighborhoods, people drive less and, so there's a lot of evidence to support that. And so you may think, "okay, why did you need to go and do a study", but there's been this nagging doubt, how much of this relationship is due to that type of self-selection that you just talked about, and how much is a causal impact? How much is people who like to walk or leftover bus moving to walkable transit-rich neighborhoods, and how much is the built environment itself, exerting a change on how people decide to get around. And then what I think is particularly missing from literature, is the role of parking. And it seems to make sense intuitively that if you have more parking built in a building, people are going to own more cars, and people are going to drive them up. But that's really hard to demonstrate in practice for a couple of reasons. First, the data, density is really easy to measure and obtain, parking data is a notorious pain to get, and to manage, like very few cities know how many parking spaces there are in their buildings. Many, even transportation planners who should know better, do surveys that don't even ask people how many parking spaces are in the building or are about to add parking at work. And then secondly, the self-selection problem, says certainly happen at a neighborhood level, you choose a neighborhood based on how good the transit, it's walkability, it's car accesses. But there's lots of other reasons why people choose neighborhoods, could be schools, proximity to friends, family, everything else whereas parking, it's much more granular, it's at the building level. So if I have a car or two cars, I care much more about parking when I'm looking for somebody to buy or to rent. If I don't have a car, then I'll go for the cheaper apartment that doesn't come with parking, if that's available, And to the extent that the market provides that, and this is somewhat of a sidebar or my one of my gripes so far about Los Angeles and someone looking for housing Los Angeles, it's so difficult to find (an) apartment that has less than two parking spaces, or even no parking spaces at all. And for me, as someone who doesn't want that second parking space, I resent having to pay for that.

Shane Phillips 9:59
Yeah, but that's the key, as a housing and a transportation researcher, you understand that you are paying for it, whether it's a separate charge or not. It's just the cost is baked into your rent. So that kind of gets at my next question here. You know, this is the UCLA Housing Voice podcast, we're not focused on transportation, even though we really care a lot about it. So why as housing researchers, as people interested in housing affordability and access and these other things, why should we care about this question of what influence parking and the location of housing and it's built environment has on the way that people get around?

Adam Millard-Ball 10:42
But from the housing point of view, transportation is one of the factors that drives housing costs, and hope Mike can weigh in little bit because this speaks to much of his own work. But many of the infrastructure costs loaded on to housing developers. And so if you think there's going to be more traffic, or you think parking demand is going to be higher then cities ask the developer not just to provide more parking, but perhaps to widen the street, or to widen the intersection at a turn lane as a condition of approval to signalize intersection. And so to the extent that traffic impacts inflated for new development, that drives up the cost of that housing, because it's forced to pay for much of that infrastructure. And then there's also just general public policy reasons, I think, to care about the impacts of policy decisions in order to do a better job of planning in the future. And then it also affects the design of grant programs. So some fundings and grant programs increasingly are tying housing funds to reduce climate impacts to reduce car travel, this type of study, I think, is important in helping refine their methods and criteria.

Michael Manville 12:02
Just to add to what Adam saying there, which I think is exactly right. You know, particularly with respect to parking, it's the parking requirements that are put on housing, especially housing that would otherwise be infill, is often what we call the binding constraint on density, you know that there's plenty of examples throughout cities across the US, where you have a parcel that if you look at the allowable density, and the FAR, or you could say, "oh, well, you could put 15 or 20 units of housing here". And then you realize that because of the parking requirement, either your budget or the site geometry, once you accommodate that parking, actually, you can really only put 12 units of housing or 14. And so what's really reducing the housing supply is that parking requirement, and to a certain extent, that's a little bit harder, I think, to quantify these other situations where, for instance, you surrender some land to widen the street or widen the intersection. And you can have a, I think you can have a beef with that on two levels, right, you know, the, the justification of these mitigations, the parking requirements and so forth, when it is spelled out. And it's these rules have been in place for so long that at this point, often they're not spelled out, they're just there. But when it is spelled out, it is this assumption that you're going to put this building there, everyone's going to drive and when they drive, they're going to congest the street, they're going to congest the curb, and so the developer has to accommodate that. And on one hand, I think in a better world, we might be able to say, "well, so what?" right? Like it's okay, if a housing development goes in, and the street gets a little bit more congested, right? I mean, maybe we prefer that you have denser development, and we're willing to tolerate more congestion.

Adam Millard-Ball 13:49
It's a transportation tale that just keeps wagging the housing dog.

Michael Manville 13:53
Exactly, so maybe we should flip that around and housing should become the dog that controls its tail. But even if you don't, if you don't accept that, and you say like, "No, I mean, the transportation tail should continue to be the influence. I think the findings that we're going to discuss and that you know, or have been hinted at prior to Adams research, but that he maybe demonstrates more conclusively is that actually, even if you worry about development creating more driving and new congestion, it turns out that these mitigations are perverse, right? That putting in more parking, and widening the street doesn't mitigate the sort of fixed amount of vehicle travel that would have happened, it actually encourages more of it.

Shane Phillips 14:38
Right.

Michael Manville 14:38
Right, and so even even on the terms that a development opponent might frame this, our understanding from Adam's research and other research like it is that "well, no, you know, even from that perspective, this is counterproductive". I think maybe also we should talk about... there's two things going on when we talk about this selection bias question. There's this issue of 'are people finding the housing they want' right? Like if I'm someone who just doesn't really want to drive or like Adam was saying he's someone who arrives in a city and doesn't want two parking spaces, does the built environment as i'ts constructed right now, let me satisfy that preference. And the fact is that in a lot of the country right now, if you're someone like Adam, who doesn't want those two parking spaces, it doesn't. And so there's a, there's a potential thing going on with Scylla, when we talk about selection bias, that saying, "Oh, you could build housing like this", but you're not going to change anyone's behavior, what you're going to do is redistribute people who just didn't want to travel in a particular way away from housing that didn't suit them and towards housing that does. And then there's an extra level that I think really is much more of the obsession of the social scientists, which is, did you, with a good identification strategy, demonstrate that you took someone who in any other circumstance would be behind the wheel of the car, and make them into a pedestrian. And I would like to hear Adam talk about this a little bit more, because I think, you know, for a long time, self-selection just dominated transportation seminars, like you could just read someone, and if you weren't paying attention in a presentation, you can raise your hand at the end and still sound smart and be like, well, what about self selection?

Adam Millard-Ball 16:25
It's like, you just want to make a comment that tries to undercover speaker and you say, "haha, but have you thought about some selection?"

Michael Manville 16:33
Exactly, right. I mean, it was just, it was a way you could space out and still kind of like come in with a zinger at the end, because that's what petty academics do. But I think if you're not an academic, you could if not an academic, you might not think about this at all. But you could think about it and then say to yourself, "well, I wonder how much this matters, right?" Because if we do have a shortage of housing development, that's, you know, amenable to people who don't want to drive much, like, does it matter if what we're doing is just helping those, this pre-existing group of people who don't want to driv, find a place where they don't want to drive?

Shane Phillips 17:06
Right

Michael Manville 17:06
Or is it really extra important to say, "No, this was gonna be a driver, and now she's a walker". So I don't know, I'll let Adam take that away. But I think it's a question that sort of it has been kicked around for a long time.

Adam Millard-Ball 17:18
I agree completely. And I think there are two separate, related but both important questions in themselves. And absolutely, I don't think it's that controversial to say that public policies that make people happier are a good thing.

Michael Manville 17:36
Take it back.

Adam Millard-Ball 17:36
And so if some people like living in a walkable neighborhood and don't want to pay for a second parking space, or any parking space, and they don't have access to that housing right now, than building more of what people want, it's absurd that cities are standing in the way of that, and forcing developers to build products, which really not what people want. I mean, this as concerns, say, like building safety, or things like that, right?

Shane Phillips 18:06
It's sort of like a two-step or two-phase issue, or it's like, "let's first just satisfy everyone's existing demand". Like we're not even there yet, and so this question, while important of like, for people who have different preferences, is this enough to change their behavior in ways we deem socially beneficial? Like, it's an important question, but it only becomes really important, I think, after we've built enough of this type of housing, so that people who have a preference for walking more, biking more taking transit more, I realized, I'm sort of undercutting the importance of your findings here, as we're talking about, but like, it is really important yeah.

Adam Millard-Ball 18:44
I'm gonna get to that. I'll get to why I think they're important in a moment.

Michael Manville 18:47
And I mean, it's not so much that you're undercutting it. I think you're.. I guess one way to put it is that in the situation that a lot of cities are in, the the causal mechanism is very important. But a lot of progress could also be made just working within a framework that we have a lot of unsatisfied preferences. But both matter.

Shane Phillips 19:09
Yeah.

Michael Manville 19:09
And, I think that one reason Adam's research becomes important is because of course, I'll let him explain why he thinks it's important too, but one reason that I think it's important is that when we start talking about the causal relationship, one of the big questions that comes up is sort of like, "well, how much causality occurs on the margin?" Right, as we as we slowly change a neighborhood, as we slowly change the kind of environment people are in because most people, if you just kind of explained it to them, at an extreme, they understand, right, you talk to someone who lives in Iowa, and they took a vacation with their family in Manhattan. Well, the built environment turns them into a walker, right? They probably don't have to think about it, but if you ask them you just say "well, why didn't you rent a car when you got there?" And they'd be like, "Oh my god, like it's there's a stop sign every 100 feet, the parking costs of fortune, the traffic's awful. It's just so much easier to walk". It's like okay, well, there you go. Like in every other aspect of your life, you drive everywhere, we drop you in Manhattan, (and) you walk. But then I think the question that that person would have, and that we sort of have as researchers is, well, Manhattan's kind of far out there on the spectrum, you know, how much do we have to change the typical American environment before we start to see some of these behavioral changes. And that's where I think causal research, the kind Adam does, starts to really shed some light.

Adam Millard-Ball 20:29
Yeah, and I think that difference between the marginal changes and the melodic changes are really important, because certainly, the market is telling us right now that there's a shortage of walkable places with less parking, but it's so expensive to live anywhere close to transit. I think that, I don't want to sound like an old grump, and say, like planners today have it so easy, but when I was starting out in my planning career, like there was a lot of anguish about like how to get developers interested in providing like, products with less parking and close to transit. And like how to give developers various incentives, so anyone would even make give you the time of day. And now it's pushing into an open door. So the developers wanting to provide it, people wanting to live in these types of places, and the obstacle is really cities and zoning codes and other requirements. So it's pushing against an open open door. Then what I think the causality is, is important to demonstrate is that well, what happens when you run out of people who kind of want to live in center city, is it something that can move the needle by 1% or 2%, or can this mean something like five or 10 or larger percent increase if we start kind of running out of the transit geeks, and kind of the 'no car advocates', and people who are ready market for this type of product right now. And then also think just defusing, whether you or not, you think it's justified, like defusing the arguments of those people who just will say, well, self-selection, and can it discount the research? Well, that's academically but also minecraft practitioners. And that has infused them as well, that kind of maybe being much more skeptical than they should about some of the findings of a land use transportation literature, and especially about parking. And you see this all the time that, well people are still going to drive, that's like the number one license, that you build this with parking, people are still going to own cars, people want to own cars, it's not going to change then this study shows that yes, it does.

Shane Phillips 22:39
Yeah, that's really helpful. So we've got a lot of evidence that living in a place with better public transit or less parking is associated with more transit use and less driving. But as we've said, the evidence for a causal relationship is much weaker, because of the selection bias problem. In our last episode, we talked with Beth Shinn about a randomized controlled trial of different interventions to address family homelessness. And in an ideal world, you could do the same thing here, sort of randomly assigning people to different built environments and seeing how their transportation choices differ based on the type of place they live in. Tell us, I think this is kind of obvious, but tell us why an RCT isn't realistic here and how you took advantage of San Francisco's affordable housing lottery program to get around that problem.

Adam Millard-Ball 23:28
So suddenly, randomized controlled trials, that would be the gold standard for any scientific or social scientific quantitative research. That's how we know that COVID vaccines work, for example. And so while medical and physical sciences have been really the domain, until recently, of randomized controlled trials, increasingly, social scientists are using them as well. And there's some things that you can randomly assign in a straightforward way. Voter outreach is a good example. You can go and knock on some people's doors, and you give them a message and you don't knock on other people's doors. And then you see which people turn out to vote. But most of the time, much to my chagrin, it's not ethical or practical, or usually neither to do this. And in particular, with housing research, you can't ethically or practically assign people randomly to homes or to workplaces

Michael Manville 24:32
Not without that without great difficulty, right?

Adam Millard-Ball 24:35
Not without great difficulty.

Michael Manville 24:36
Exactly.

Adam Millard-Ball 24:37
Whereas this is one of the few instances where lotteries are not just feasible, but they're also ethical if you have a scarce public resource. How do you manage that? Well, you could do a waiting list or you and there's many housing waiting lists in the country and abroad, or you could do a lottery. And so that's what we took advantage of in this study that San Francisco's affordable housing program. It has immense demand for below-market rate housing in San Francisco. And so the program, even as it's scaled up can only satisfy a small proportion of its applicants. So this lottery, while it's not technically randomly assigning people to buildings is doing it as good as random. So it's a natural experiment, which is randomized, but in practice, it's as good as random assignment. And that's because it's the research upside of a really sad situation that housing is so expensive, that there is so much demand for this housing. So across all the lotteries, it was just over 1% success rate. So just over 1% of applicants for each individual lottery were successful. And some of these border on the absurd like, because you have a situation with 95 units being essentially raffled off. And there's more than six and a half 1000 applicants for vouchers for those 95 units. And so that means that people can't be that picky if they want housing and so that if you win one of these lotteries, venue, then you're really unlikely to say, well, you know, "I want to wait for the one with parking, or I want to wait for one with transit" because it's really unlikely that you're going to win that lottery twice.

Shane Phillips 26:29
And that's sort of the different treatment groups here is you have some buildings that have no parking at all, and are in places with really good transit, other buildings that have you know, a moderate amount of parking, maybe half a space per unit or a quarter of a space per unit and others that might have, you know, one or more spaces per unit, and people are being, as you say, as good as randomly assigned to these different buildings within the city.

Adam Millard-Ball 26:54
Exactly. People are being randomly assigned effectively, to neighborhoods where different walkability with different transit and to buildings with different amounts of parking. It really shows that even though it took a while to filter through to the housing stock, the impact of San Francisco's parking reforms actually made this possible were removing parking minimums, allowed some developments of our parking to go ahead, and others became a half a space three-quarters of space, in some cases, one space a unit.

Shane Phillips 27:26
So your hypothesis going into this is that the built environment will influence people's transportation choices, independent of their personal preferences. So if you had two people who were the same in every way, and you assigned one to a building, with no parking in a neighborhood with great transit, and the second person to a building, with lots of parking in a neighborhood with bad transit, the first person would use transit more, and they would drive less than the second one. What did you actually measure to test out that hypothesis? And what did you find ultimately?

Adam Millard-Ball 27:58
So the nice thing about both randomized experiments and also natural experiments like this, is that once you have this natural experiment, the research process is actually much simpler in most cases. So we just simply did a survey of the residents, these buildings, and we're working with the San Francisco Mayor's Office of Housing and Community Development, and they were great partners, and we couldn't have done it without their buy-in and in cooperation. So we send people postcards, where we had email addresses, we send them a link to an online survey in foreign languages. And so we asked people about how many cars they own, how they get around, have a commute to work, and also about their employment. So we tried to give a survey really simple so that we wanted more responses, even at the expense of less complex surveys. And so we got nearly 30% response rate, which is beyond what I was hoping for, it's a pretty famous type of survey.

Michael Manville 29:03
That's great.

Shane Phillips 29:03
So what was the effect and sort of how big was the effect based on you know, transit quality, and the amount of parking in these buildings.

Adam Millard-Ball 29:12
So there's an effect so that was the first order of business, it was measurable And which for the self selection crowd might not have been quite as obvious and especially for the packing self selection crowd might not have been as obvious and that moving someone from a less walkable to walkable neighborhood or from a building with parking, to one without parking, it changes how they commute, have a travel for other trips and how many cars they own and so yeah, you might say that's not surprising, but the people who think that the whole effect of the built environment is because of self-selection, and hopefully goes some way to convincing them that self-selection is not a whole story. And then in terms of the is this a Vegas Well, it depends on what you think is is big, but it's certainly measurable. And it is I think it's substantively important that say, if you move someone from the transit accessibility as out of sunset, that's really suburban neighborhoods with lots of parking not great transit, in San Francisco to Potrero Hill, which is in a suburb, one of the kind of denser inner rings. And that's actually of a city wide median, there's a 6.5 percentage point increase in transit much rather than big car.

Shane Phillips 30:36
That's pretty big

Adam Millard-Ball 30:36
that's a big, that's a big effect. And not even to the extent from one extreme to another from a pretty codependent neighborhood, but there's still some transit to one that's just at the median of the city.

Shane Phillips 30:49
And you were actually looking at the metric of transit quality on the one hand (transit quality, accessibility, whatever you want to call it), and then parking in the building on the other. And obviously, those combine, in some sense, but correct me if I'm wrong, but the impact of having less parking in your building was greater. So that increased transit ridership more than improving the quality of the transit actually,

Adam Millard-Ball 31:15
Absolutely, and that was perhaps the biggest unexpected finding for me was just how dramatic that comparison was that parking mattered more than twice as much as transit in determining whether people take transit or drive. And so that these be sticks in terms of like making car use less subsidized and have a bigger impact, than the making transit frequency and accessibility better.

Shane Phillips 31:45
Yeah, and I think it's worth emphasizing that that's a pretty consistent finding with previous research that actually making it harder to drive, including harder to park seems to have a greater impact on the way that people get around, than improving the quality of transit does, which is a little, I don't know, kind of disappointing, in a way. But I think that's pretty consistent. Mike, maybe you have some other examples you can point to of that. I'm thinking of like the parking cash out, which is sort of an example of that. But I know there's others.

Michael Manville 32:16
Yeah, there was a great paper, maybe seven or eight years ago that Dan Chatman at UC Berkeley wrote about transoriented developments that the title was 'Does Todd need the T', which basically said that actually, if you just had a kind of a dense walkable neighborhood, it almost didn't matter if there was in his example, a rail station there, because you would actually see, you know, more walking and more moving around outside of a car, and less vehicle miles traveled just because of that built environment. And I think, you know, it might be, I guess it could be, interpreted as being sort of discouraging if you're a transit junkie. But if you're just someone who is interested in, you know, different ways of moving around, it's quite encouraging, just because a lot of transits very expensive. And it suggests that, you know, there's a lot to be done. And there's a lot that can be accomplished, just by getting people to sort of implicitly rethink their choices, short of sort of reorganizing the entire neighborhood. None of it should be interpreted, in my opinion as an argument, against more transit.

Shane Phillips 33:24
Right, right.

Michael Manville 33:25
We're just saying, like, look, you know, a lot of us, we don't realize the extent to which the car is sort of artificially low priced for us. And we don't realize the extent to which we hop in the car when there really are other things we could be doing even in a car oriented environment, you know, Could I could I walk down the street to the store, could I bike over to see my friend, and just changing that calculus a little bit can change travel behavior in ways that uh, that don't need to require sort of like extending the bar or something?

Shane Phillips 33:56
Yeah, and it's actually it's funny because extending the bar adding new bus service, these are expensive things they're worth doing but they do cost money. Building housing with less parking not only doesn't cost us any money, but it also saves tenants and homebuyers money so it's actually costs us less than nothing.

Adam Millard-Ball 34:16
Picking up Mike's point about cost subsidies I think the dynamic just goes to show just how easy it is and cheap to drive by car and how hard it is to compete with that for the transit.

Michael Manville 34:30
Exactly

Adam Millard-Ball 34:30
And if you are fighting or trying to compete with a mode that there's no parking costs that are charged to you and the gas is cheap for you get priority on the road, and you don't even have to stop for pedestrians or crosswalks...

Michael Manville 34:52
That's right.

Adam Millard-Ball 34:52
... It's how are you going to compete with that, like how good transit is, it's an uphill battle, and that's why I think The research shows that even really modest charges, were like $1 a day for workplace parking, or slight changes in car access had a much bigger effect than improving transit. Because even if we doubled the frequency of transit, it's still gonna be slower than taking the car in most cases.

Michael Manville 35:19
That's right. I think, you know, there's something about a price that's, that's zero, that you know, that this is why zero is a special number, right? It's, a special number mathematically, you can't divide into it or whatever. But it's also I think, psychologically, if something is really priced to zero, you don't have to be at all mindful about it. And even if it is just $1, suddenly you think about it in a way that you didn't think about it before. And Adams, you know, I guess we're feeding off each other here. But this point, it really is worth emphasizing about the artificial cheapness of driving and we're gonna just the podcast is now UCLA Transportation Voices. Take us into it. I mean, just because right now in Los Angeles, and in many other places, there's a there's a lot of discussion about, in Boston as well, should we make transit free and get rid of fares, and, you know, there's good and bad arguments for that. And I won't weigh in on it, other than to say that the big obstacle to transit use in the United States is not the transit is expensive, right, because transit is already heavily subsidized. That's not to say there isn't the case for subsidize it even more, it really is that the other alternative is so cheap and convenient, right, that the big obstacle is not that it costs $1.75 to get on Metro. It's that if you have a car in Los Angeles, chances are you have free parking where you live, you have free parking, where you work, you have free parking where you shop. And even if it was free, that's probably what you do. And so it really is sort of the relevant price that dictates the mode choice is just, it is beyond the fare box of the transit system.

Shane Phillips 36:58
Yeah. Adam, do you find it surprising how big of an impact the built environment has here? Or maybe, you know, surprising isn't the right word, I guess I find it kind of encouraging that these relatively small changes in the places that people live can lead to pretty large shifts in mode choice. And, you know, of course, all the economic and environmental and other benefits that come along with that. I feel like we're led to believe that people are pretty set in their ways, and the behavior is hard to change. And I think in many cases, that really is true. But maybe the reason that doesn't apply as much here is just because we're catching people when they're already sort of in the midst of a big life change almost by definition, because they're moving. As someone who spends more time thinking about transportation than I do, I'm curious to hear some of your reflections on just what this represents for the future of cities more generally, you know, meeting our climate goals, anything else in that vein?

Adam Millard-Ball 37:52
Sure. I think this is narrative, which I hear from the public, I hear from my students, I hear everywhere that Americans just are in love with their cars, and they will drive regardless of anything, and that Americans are special in that regard. But you know, I lived in the UK, I live in Canada, like people there kind of like their cars, too. And you can make the same argument. And while there might be some people who are kind of really into the car design or something like that, I think that there's a much bigger room for people who are just, they love their cars, because they're usually cheaper and quicker to get where they want to go. And so making even modest changes to their relative costs and speeds of cars, compared to the alternatives, it's not surprising to me that that has impacts on travel behavior. And that's what I was most surprised of was the findings on how much a building's parking supply, or parking ratio, affects car ownership and travel because these buildings are banning people from having cars. There's plenty of parking in San Francisco in other places. And there's a really healthy secondary market, you can go on Craigslist, and you can rent a space for a couple of hundreds a month. You can park on the street if you're willing to move it every week for street cleaning and pay a token a man for a residential permit. So even these parking-free buildings, they're not car-free. And many of the people who lived in these parking-free buildings, actually 38% of our sample, they still had a car. So it's not stopping people who need a car for various reasons, or are really attached to their car from having one, it's just making it a little more difficult, a little more expensive, and a little slower because maybe rather than just riding (to) your building, you have to walk five minutes down the street to the space that you rented.

Michael Manville 39:55
The other thing I want to emphasize about Adam's study is that one could listen to what we said so far and say, "oh my goodness, well, but you're just studying a bunch of people who want below-market rate housing, you know, of course, they're not going to drive that much. They're low income". And this is the tragedy of San Francisco, right, which is that it's so expensive, that even fairly simply, by many standards, very affluent people can enter these lotteries, right? I believe the cutoff for entering an affordable lottery in San Francisco is over a six figure household income. And so this is not, I just want to make sure our listeners understand this, we do not have this sort of potentially non generalizable sub sample where we're studying very low-income people who need subsidized housing. And so obviously, they're always looking for a way not to drive, they naturally ride in transit...

Shane Phillips 40:43
.... and $200 for a parking spot everyone would be, you know, unattainable.

Michael Manville 40:48
A tremendous burden. I mean, there's, you know, there's some attorneys in this mix, probably right. And so that's important to understand. And..

Shane Phillips 40:55
I don't think an attorney is taking a job for under six figures in San Francisco, though

Michael Manville 41:00
There's some there's some bad attorneys, kind of bottom in the class at Berkeley, great, but that's a fair point. The other thing I want to say, which is, you know, it was related to Adam's point that almost 40% of the people they did study did have automobiles is that, you know, people get surprised by these impacts. And I think that's understandable. But part of the beauty of this, and that's sort of hard to appreciate, is that you can get a lot of really meaningful changes in people's behavior, without having to turn their lives upside down right? I think there's some times in the public discourse around this, there's this idea that you're going to build a house or build an apartment, some of the housings not going to have parking. And so for that, to do any good at all, the people who move in have to just turn into, you know, freakish, earthday people who like would never get in the car. And certainly you do get a lot of bang for your buck and reducing VMT, if you do tip someone who was going to own a car into not owning one, because once you don't own a car, you really don't drive much at all. But as he was saying, if you just now live in a situation where you have to walk five minutes to get to your car, there's probably a lot of daily things that are within a five minute walk of where you're going. And so suddenly, you're just not driving for that trip, right and over a lot of people and a lot of time that adds up. And what doesn't even seem like a big change to you. But it is on a neighborhood level and sort of an aggregate level a large change in sort of how much people are driving and how much right people are using their automobiles.

Shane Phillips 42:36
Yeah, and I know, Adam, you probably didn't get to this level of specificity in your survey. But I imagine a lot of the residents who responded and who moved into these affordable homes, they probably moved in with their car, even if it didn't have parking provided. And it might have been sort of over time, they didn't sell it the instant they signed the lease, they might have just kind of realized over time, you know, this is inconvenient, I can get around these other ways. And you know, two months later, six months later, maybe by then they don't have a car. But that's not you know, it was just a transition that made sense. It wasn't necessarily this immediate decision, changing their life on the turn of a dime.

Adam Millard-Ball 43:19
We didn't get into that in the survey. But absolutely, that's reasonable to expect. But the first parking ticket is annoying is annoying. After the third parking ticket you get in a month, then you just want to be done with your car.

Shane Phillips 43:33
So I was pretty surprised to learn that the people assigned to the buildings with less parking who drove less, on average, were still just as likely to be employed full time. I think a lot of us advocates for better public transit and fewer parking mandates, really fervently wish that transit was just as good at providing good access to jobs as cars are. And they certainly can be if we invest enough in it if we give priority on the streets to buses, and complement it with the right land uses. But compared to driving in just about every place in the US right now. I think this is mostly true of San Francisco even as well. It's unfortunately just not the faster option and doesn't connect you to nearly as many jobs, transit compared to driving. Our colleagues here at the Lewis Center, including our director, Evy Blumenberg, and our very own co host here, Mike Manville, have done quite a bit of research showing how important car ownership can be for low -income households' economic prospects, and access to jobs, all the more so in a place like Los Angeles. So since you didn't find any impact on employment, you know, why do you think that was? Is it just a matter of San Francisco having unusually good transit access compared to most other cities? Or do you think there might be some other explanation here?

Adam Millard-Ball 44:50
So certainly, we did the survey at a time when unemployment was really low in San Francisco in particular, but also nationally, that also I don't think these findings are incompatible, because we're studying the effect of having parking in a building not on whether someone has a car. And as we just talked about, there's lots of other ways to have a car in a parking-free building, you can rent a space nearby you can, you can park on the street. And if you are in a job where you can't get there by transit, or you're working night shifts, maybe a transit may not run or feel safe, then there's no reason you can't have a car, it's just a little more inconvenient. And maybe you're paying extra for their parking space, compared to if you hadn't lived in a building where parking was bundled in with the rent or the the sale price. So not providing parking isn't the same as everyone in the building not having cars. And again, nearly 40% of respondents who lived in buildings of our parking actually did have a car, we didn't ask where they parked. But again, there's this healthy secondary market in parking in San Francisco. And it all is essentially a nice segue into one of my gripes with the way that cities often planned for buildings that have less parking, that they then go and say, well, as a condition of this, you need to prohibit the residents from having a street permit, which goes against that flexibility and is entitled to that street space, treat space as much as anyone else. And almost have the greater need for that to provide that flexibility. But so someone gets a job or has some other change in particular personal circumstances. That mean they need to have a car for my forces person to move just because you want to reserve the street space for someone else. So we understand why cities do that for kind of expediency for perhaps overcoming some local opposition. People are worried about parking impacts, but from a policy and from a basic human dignity perspective, it seems really misguided to me.

Michael Manville 47:08
You know, Adam's answer is absolutely correct. And what I would add to it is that, you know, Adam has shown that if you put some people in particular environments, some of them might realize they can do without a car. And I think the way another way to think about why that's compatible with Evy Blumenberg's work, Mike Smarts' work, (and) some work I've done with like, and Evie and Dave King, is that right now in the US, if you see someone outside of New York City or San Francisco, that doesn't have an automobile, I mean, there's a good chance they're a very low income person, or they have some sort of medical condition that prevents them from operating a car. And they suffer low mobility as a result of that. Right, so right now, if you see someone who doesn't have a car, chances are they could use one. But the other side of that, right is that right now, there are lots of people who have a car that they could probably do without. So I have an example. I own an automobile, it's fully paid off. I have an apartment building in West Hollywood, a bundled parking. So if I got rid of it, I would save nothing on my rent. And I use it. Sometimes I like to go hiking, I take my dog places I like to go skiing. And so I have this car, right? But if I gave it up, I would not lose my job. I would not see my income reduced, I would suffer some minor inconvenience right? And so the reason these two it, I think it's important, right? There's, there's a lot of people in the United States who have a car, they don't need. There's an even larger number of people who have a car and use it more than they have to. And that's a different problem than that there's actually a pretty small proportion of people in United States who don't have an automobile and whose life would be changed if they had one. But the way to help those people is to identify them and get them some help not to look out over the the vast expanse of America's built environment and mandate parking. Yeah, right. That's a very inefficient way to help a very small number of people who really do need some direct assistance.

Shane Phillips 49:15
Yeah, for among other things, they need the car, not the parking.

Michael Manville 49:19
Yes. Right.

Shane Phillips 49:20
So as we wrap up here, is there anything we missed in the paper that you wanted to cover any any key points here?

Adam Millard-Ball 49:27
The big point that I want to emphasize, and that you touched on the start is that this is very 20 really good reasons to create more walkable neighborhoods and provide choices in how much parking both residents and developers have to have. And while I think that the travel behavior side is really important, I think that work of Don Shoup and Mike Manville and many others has shown that you know, there's really no good reason to have packing requirements, even if there were no travel behavior impacts. So in many ways, this is just kind of a bit of a pile on to, I mean, not beating a dead horse because the horse is still really much alive and kicking for...

Michael Manville 50:12
God that horse is alive.

Adam Millard-Ball 50:15
But we only had enough evidence for why parking requirements are a bad idea. But perhaps it is going to one more study that just pushes up, I Imagine, that, you know, parking policy is a great way to address issues of, say traffic and, and transportation. But we shouldn't forget that it's also like a really important way to address issues of housing affordability as well.

Shane Phillips 50:46
Adam Miller-Ball, thank you so much for being on the show.

Adam Millard-Ball 50:49
Thank you.

Michael Manville 50:50
Yeah, thanks. It's been great.

Shane Phillips 50:56
You can read more about Professor Millard balls research and find our show notes and a transcript of the interview at our website lewis.ucla.edu. The UCLA Lewis Center is on Facebook and Twitter. I'm on Twitter @ShaneDPhillips. And Mike is that @MichaelManville6. Thanks for listening. We'll see you next time.

Transcribed by https://otter.ai

About the Guest Speaker(s)

Adam Millard-Ball

Adam Millard-Ball is an associate professor of Urban Planning at the UCLA Luskin School of Public Affairs. His research and teaching are about transportation, the environment, and urban data science.