How Congestion Pricing Can Impact Human Health

IRA FLATOW: In early June, New York Governor Kathy Hochul blocked a congestion pricing plan from going into effect in New York City. Now, this plan would have required cars to pay a fee for entering the central business district of Manhattan. Congestion pricing helps to discourage people from driving into city centers to reduce traffic, but it does more than just keeping cars off the road.

Fewer cars could mean fewer greenhouse gases, which could mean better air quality and a healthier population. Now, these positive impacts have been shown to work in other cities around the globe, like London, Stockholm, and Singapore. But how exactly would that translate to New York City and other US cities?

Here to tell us more about the health impacts of congestion pricing are Janet Currie, co-director of Princeton’s Center for Health and Wellbeing, and Andrea Titus, assistant professor of the Department of Population Health at NYU’s Grossman School of Medicine. I’d like to welcome you both to Science Friday. Thanks so much for being here.

JANET CURRIE: Thank you.

ANDREA TITUS: Pleasure to be here.

IRA FLATOW: Janet, I’d like to start with you. Maybe you could just tell us where this idea of congestion pricing comes from in the first place.

JANET CURRIE: Well, it’s a very old idea, really, in economics. A Nobel Prize winner named Vickrey came up with the idea. And the idea is to use the market in order to induce people to do something socially beneficial.

So if you have a congestion cost of driving into lower Manhattan, only the people who value going there the most will pay. And so then you’ll allocate the pollution across people, so that the ones who benefit the most from causing the pollution will be the ones who actually do it.

IRA FLATOW: So how exactly, Andrea, does this then impact the health of people in the cities where it’s implemented? What are we seeing largely in the places where this has happened?

ANDREA TITUS: Sure. So the health outcomes that have largely been studied fall into a couple of different buckets. One is looking at the impact of congestion pricing policies on road traffic incidents. So these are things like car crashes, bicycle, or pedestrian injuries.

So by changing the flow of traffic, changing the number of cars that come into the congestion zone, that has been shown in other cities, over time, to be associated with lower rates of road traffic incidents. The other set of health outcomes that has been studied are associated with improvements in air quality.

So we would expect that a congestion pricing policy that decreases the number of cars driving into the congestion zone would lead to lower levels of traffic-related air pollutants. Also, just by addressing gridlock directly, we expect improvements in air quality because any time cars are in stop and go traffic, they’re releasing more pollutants.

So both by reducing the number of cars coming into the congestion zone and also making the traffic flow more efficient, we expect to see improvements in air quality. And those can translate into health outcomes. Largely, what’s been studied has been health outcomes associated with cardiovascular disease and also respiratory disease, like asthma.

IRA FLATOW: So Janet, you have studied the health impacts of congestion pricing in Stockholm, Sweden. It’s a city that’s had this implemented for several years. What did you find?

JANET CURRIE: So we looked at Stockholm, and they did a very interesting thing. They had a trial period for six months. And then after the trial, they had a year where it went back to normal in terms of the traffic. And then they implemented a permanent congestion pricing regime.

So what we found was that, initially, we had a reduction in visits for acute asthma among children 0 to 5 of 16%. But then the effects got bigger when the congestion pricing became permanent. And we had a 50% reduction in acute asthma visits in Central Stockholm compared to other central cities in Sweden, which didn’t adopt congestion pricing.

And what we found, also focusing on the youngest children, was there we got the biggest effects. And so what we thought accounted for the big, long-term effects was that we were actually, by implementing congestion pricing, preventing some children from ever getting asthma at all.

IRA FLATOW: Has anything like this been tried in other cities in Sweden? And have other areas outside of Stockholm seen any positive impacts from this plan?

JANET CURRIE: So I don’t think congestion pricing has been implemented in other cities. They tended to have somewhat lower pollution levels to begin with. And the Swedes have been doing a lot of other things to reduce pollution, such as encouraging electric vehicles.

So pollution has continued to decline in Stockholm since this. And I think it’s a kind of multi-pronged approach. Another thing they did was actually to get rid of studded tires because, apparently, studded tires just by themselves cause a huge amount of particulate matter that comes off of the tires.

IRA FLATOW: Well, maybe you can just talk for a second, though, about what particulates we’re talking about. I mean, I think we all get a sense that air quality is bad whenever you can smell a lot of exhaust from vehicles. But what types of particulates are in the air that a program like this is trying to get out?

JANET CURRIE: So what people focus on is what they call PM2.5, which is basically very small particles. And it could be very small particles of anything, dust, toxics, and so on. But when you burn fossil fuels, you get carbon. You get nitrous oxides. And you get lots of soot, like little tiny particles.

And the reason why people worry about the little tiny particles is because they can get into your lungs. And then once they’re in there, they just stay there and cause inflammation, which then causes all these other problems like heart conditions or asthma.

IRA FLATOW: Gotcha. And I can only imagine how that’s really bad for young kids. So Andrea, I want to talk about your study looking into the potential benefits of congestion pricing in New York City. Again, a plan that has been paused for now. How does that compare to the expected effects it could have on the health of New Yorkers? I mean, what have you found in studying this prospectively?

ANDREA TITUS: Sure. So what we know about the potential impacts of the policy comes from projections, simulations, modeling studies. And this is not my work that I’m citing specifically here. But we know that before the pandemic, for example, approximately 700,000 vehicles would enter the central business district daily on average.

And this policy is expected to result in 100,000 fewer cars and vehicles entering the congestion zone every day– at least the policy in the way that it’s currently articulated and set up. So that could translate into different kinds of health outcomes. There was one simulation study that projected approximately 750 fewer auto-related crashes per year due to traffic flow changes associated with the policy.

There have also been several simulations that have tried to project what might happen to different kinds of air pollutant levels within the congestion zone. So thinking about PM2.5 or fine particulate matter, for example, most of the simulation studies would estimate reductions of PM2.5 within the congestion zone of around 5% to 12%. Some studies have it a little bit higher than that.

And just to put that in context, that’s very much in line with improvements in air quality that we have seen in other cities like in London and Stockholm that have implemented congestion pricing policies and seen the health benefits associated with those policies.

IRA FLATOW: So this study, though, also mentions some of the issues around racial and wealth inequality as something that should really be looked at further before a congestion pricing plan goes into effect in New York City. What can you tell me about that?

ANDREA TITUS: So equity considerations are really important to a policy like this and really cuts across the policy in multiple ways. So I’ll just mention one example of this that’s gotten a lot of attention. So we might expect with a policy of this kind that there would be some amount of traffic diversion. So to some degree, some cars, or vehicles, or commercial trucks that would have driven into the central business district may choose to drive around the central business district to avoid the toll.

And the concern from an equity perspective is that some of these circumferential routes, some of these routes that someone might take to avoid the tolling scenarios, cut through parts of New York City that already face really high amounts of environmental burdens and environmental risk factors that already have poor air quality or high rates of things like pediatric asthma.

So while most of the projections haven’t estimated that there will be a large amount of traffic diversions– this is a relatively modest amount of traffic diversions– really, any traffic diversions through these environmental justice communities would be concerning from a health equity perspective. So that perspective really needs to be front and center in the design of the policy and in the evaluation of the policy.

One other factor that’s very related to equity is the reinvestment of the funds that are raised by congestion pricing. So one major goal of this policy is to raise revenue for the transit system in the New York City region. And so to the extent that money is used to improve the transit system operations or improve the accessibility of the transit system, that also has implications for equity.

IRA FLATOW: Gotcha. So for people who don’t live in the New York City area, the idea is that if you ban cars essentially, or at least make it very expensive for cars to drive into central city Manhattan, where people certainly live, but they are not some of the areas that you’ve been talking about, there’s a possibility you might have people driving through areas like the Bronx, where some of these problems have been persisting for years.

ANDREA TITUS: Right, exactly. So there has been some modeling studies that have tried to project exactly how much traffic displacement there may be from a policy like this that would go through areas like the South Bronx, for example, or across the Cross Bronx Expressway. And for those communities, they’re already facing poor air quality and high rates of pediatric asthma. So that’s something we would need to monitor very closely with a policy like this.

IRA FLATOW: I guess another thing I should ask is– New York City is a very– well, it’s a very specific city in America. There’s probably no other place like it. And so I’m wondering what you’ve learned from this modeling that we might be able to apply to other cities that aren’t New York.

ANDREA TITUS: So we have thought about this question a lot, both in the context of what we can learn from other cities like Stockholm and London that have implemented congestion pricing, and how much of those lessons can be translated to the New York context, which is very unique.

I think that this policy is really important to study in the context of the United States. This would be the first policy of its kind that is a cordon-based congestion pricing policy within the context of the US. And there are other cities across the US that are considering similar policies.

So places like Portland, Oregon, Seattle, Los Angeles, cities that face problems with gridlock or congestion in their downtown areas are considering similar policies, and I think are watching really closely with what happens in New York City if we move forward with this policy. How is it designed? How is it implemented? And how is it going to be received by the public and different stakeholders?

IRA FLATOW: Yeah, Janet, I’m wondering how you’ve been thinking about that as you’ve studied other places and how these programs have worked, whether or not you think it could be widely applicable in US cities.

JANET CURRIE: Well, one thing I think is important to keep in mind if you think about a place like London, they’ve had it since 2003. But the program today is not the same as it was then. They’ve experimented a lot with changing the zones, changing the rates, having this ultra-low emissions special rate, and so on. So they’ve tinkered around with it quite a lot.

And as I was mentioning with Stockholm, they didn’t just have congestion pricing and then go home. They thought about all sorts of other ways to improve air quality. So I think maybe the right way to think about congestion pricing, it’s kind of a start.

It’s something that– it will be very interesting if it ever gets implemented in New York to see how it goes. But one should expect that it’s going to need to be tinkered with and added to, in order to get the full benefits.

IRA FLATOW: So something else I wanted to talk to you about, Andrea, is we’ve been talking a lot about these localized health impacts, things like asthma and even traffic deaths. These are very important. But cutting down on traffic in inner cities could also mean good news in fighting greenhouse gas emissions and climate change. What can you tell us about how these programs might work to do that?

ANDREA TITUS: So the transportation sector is the largest source of greenhouse gas emissions in the United States. So this is a policy that would contribute also to climate change mitigation efforts.

So putting policies in place that limit the amount of greenhouse gas emissions from the transportation sector is certainly part of a broader strategy to address greenhouse gas emissions. It’s not the only thing that we need to be doing, but it is an important piece of that puzzle.

IRA FLATOW: For those who think that this is a good idea and for people who think this might be a way for cities to cut down on asthma, might be a way to solve some of the problems with greenhouse gas emissions, are you worried at all that this stop of this New York program might send a signal to other places that congestion pricing just isn’t ready in the United States?

ANDREA TITUS: It’s certainly a complicated political picture. I think that there is understandable hesitation or maybe trepidation about new tolls or new fees that may be levied on drivers moving into or driving into downtown areas. So I understand that it’s a complicated political process. It’s also a bold move for an urban area to take on something like congestion pricing.

And I think we have to remember also that this is a policy that has been implemented in other cities around the world. It’s been implemented in London for decades. So we do have a really solid foundation to take this step and learn from other places that have implemented these policies, and as Janet has mentioned, refine those policies over time to meet the local context.

JANET CURRIE: It’s essentially a tax. So thinking about it like that, then it’s not surprising that taxes are unpopular. And the question would be, well, what’s both the most politically feasible kind of tax on driving and also the fairest tax on driving that you could implement to reduce traffic and also raise revenue for other things like public transportation.

IRA FLATOW: Well, I guess that was the last thing I wanted to ask you about is, is this idea of raising money to put into public transportation, so that public transportation is cleaner, safer, more available to people, it’s something that they want to use– that really is the goal of this, isn’t it, Janet?

That if more people were just doing public transportation in more cities, not just in the US, but across the world, we would really be cutting down on both localized health impacts but also on greenhouse gas emissions very quickly.

JANET CURRIE: Yes, that’s true. And New York is kind of unique in having a heavily used public transit system already, although it seems like it’s held together with band-aids and duct tape at the present moment. So it really needs an infusion of cash in order to keep moving those millions of commuters every day.

IRA FLATOW: It can be a little bit difficult at times. But I really want to thank both of our guests. Janet Currie is co-director of Princeton’s Center for Health and Wellbeing. Andrea Titus is assistant professor in the Department of Population Health at NYU’s Grossman School of Medicine. Thank you both for your expertise and for bringing this issue to our listeners.

JANET CURRIE: You’re very welcome. Thank you.

ANDREA TITUS: Thanks for having me.

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