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You can find the shownotes through this link.

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Are you interested in how removing traffic affects urban areas?

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Our debate today works with the article titled Scaling the superblock model to city level in Barcelona? Learning from recent policy impact evaluations from 2022, by Jaime Benavides, Sabah Usmani, and Marianthi-Anna Kioumourtzoglou, published in the Contesti journal.

This is a great preparation to our next interview with Ben Wolf in episode 424 talking about one street in New York that reduced its car traffic and its effects on its environment.

Since we are investigating the future of cities, I thought it would be interesting to see an urban model that curtails vehicle traffic and reclaims public space for pedestrians and greenery. This article investigates Barcelona’s Superblock model with its complex outcomes, suggesting that neighbourhood level policies must be paired with a holistic metropolitan mobility plan for traffic to be effectively reduced city-wide.

[intro music]

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Welcome to today’s What is The Future For Cities podcast and its Research episode; my name is Fanni, and today we will introduce a research by summarising it. The episode really is just a short summary of the original investigation, and, in case it is interesting enough, I would encourage everyone to check out the whole documentation. This conversation was produced and generated with Notebook LM as two hosts dissecting the whole research.

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Speaker 1: When we look at a city from above. It’s incredibly easy to view the grid of streets as a kind of cardiovascular system,

Speaker 2: right? Like arteries.

Speaker 1: Exactly. The roads or the arteries and the cars or the lifeblood pumping through them. And for nearly a century, urban planners operated on the very simple assumption to keep a city alive. You just have to keep those arteries as wide and open as possible.

Speaker 2: Yeah. The prevailing thought was always that flow equals vitality. But in reality, when you push that much sheer volume of heavy machinery through a confined historic space, you don’t get vitality. You get a heart attack.

Speaker 1: You really do. And that brings us directly to Barcelona, which is a city currently facing a massive cardiovascular crisis of its own. We’re talking about a staggering 5,500 vehicles per square kilometre in its most congested areas,

Speaker 2: which is just an immense density.

Speaker 1: It’s because of that extreme density. The city consistently exceeds European Union limits. For nitrogen dioxide mean it is quite literally a matter of life and death. So today we are looking at the policy impact evaluations of Barcelona’s radical proposed cure. The super block model,

Speaker 2: and for those who might just be picturing a regular city block, this is much bigger. The strategy effectively takes a three by three grid, so nine city blocks and turns the inner streets into a pedestrian first zone. All the heavy through traffic is blocked from cutting through the middle. It’s instead pushed out to the perimeter roads of that nine block square.

Speaker 1: My perspective today is that this Superblock model is a fundamentally transformative architectural policy that once fully scaled, will successfully evaporate traffic and drastically reduce premature mortality.

Speaker 2: And I’ll be arguing that the physical redesign of super blocks is insufficient in isolation because empirical evidence shows it merely displaces traffic and pollution to adjacent streets. Unless coupled with demand reduction tools

Speaker 1: to really unpack this, we need to look at the sheer scale of the imbalance we are trying to correct here. If you look at Barcelona right now, roughly 60% of all public spaces devoted to cars,

Speaker 2: which is wild, especially when you consider the majority of residents don’t even use cars as a primary transit.

Speaker 1: Exactly. It’s an astonishing spatial imbalance. So the Superblock model isn’t just some fun landscaping project. It is a permanent correction to the fabric of the city.

Speaker 2: But how permanent are we talking?

Speaker 1: The city’s mobility plan, along with the Utopia Health Impact model projects, something huge. If we implement the full network of 503 super blocks, we will decrease circulating passenger cars by 21%.

Speaker 2: Wait, a 21% drop just by changing the street layout, you’re saying people will just stop driving simply because the roads are different?

Speaker 1: Yes, precisely. Because you are physically removing the space for cars. The plan actually cuts allowable road space across the city by 45%.

Speaker 2: That is a massive reduction.

Speaker 1: It really is. And when you do that, you force what urban planners call a modal shift. Inside those nine block zones, speed limits drop to 10 kilometres per hour. The streets become one way loops. Cars can no longer cut directly across the neighbourhood,

Speaker 2: so it just becomes annoying to drive.

Speaker 1: Driving simply becomes too frustrating and inconvenient. So people switch to walking, biking, or public transit and the health yields from that shift are staggering,

Speaker 2: right? The projections are high.

Speaker 1: We are looking at a projected 24% drop in annual nitrogen dioxide concentrations. We are looking at preventing over 650 premature deaths every year. That translates to 1.7 billion Euros saved in health costs annually.

Speaker 2: Okay. Those numbers sound incredible on paper, but I think we have to separate theoretical architectural idealism from empirical reality. You are leaning heavily on the projection of 503 super blocks

Speaker 1: because that’s the full plan.

Speaker 2: But over more than five years of the implementation phase, how many have been fully realized? Just three pilots in Poblano San, an Tony and Hoda.

Speaker 1: They are massive, complex undertakings. Of course, they take time.

Speaker 2: I agree they take time, but we have to look at what is actually happening. During that time. I will absolutely acknowledge the local benefits. Like in the San Antonio pilot, the Pedestrianized streets saw a 25% drop in nitrogen dioxide,

Speaker 1: which is a huge win.

Speaker 2: It’s fantastic for the people living inside that bubble. Absolutely. But we have to look at the virtual mobility lab simulation, which highlights severe unintended consequences.

Speaker 1: You’re talking about the rebound effect.

Speaker 2: Reallocating space from motorized vehicles creates a massive push onto other streets. The simulation showed that while those protected interior streets get cleaner. The adjacent perimeter roads suffered up to 125% increase in traffic flow, microscopic inhalable particles from tire wear and exhaust, and embed deep in our lungs. Plus, you get a massive spike in NOX emissions, which directly trigger respiratory failure.

Speaker 1: But again, this is looking at an incomplete system.

Speaker 2: Maybe, but without an overall reduction in traffic demand, the super blocks just punish the residents who happen to live on the perimeter. The air gets cleaner for one block and highly toxic for the block right next door.

Speaker 1: Sure. But I feel like you are critiquing the concept of traffic evaporation based on a totally incomplete picture. Traffic evaporation is a proven phenomenon. It isn’t magic. Reducing road capacity actually causes overall traffic to disappear because people alter their daily habits. They don’t just vanish. They look at the map, realize the drive will be a nightmare, and they choose to take the metro instead, or they consolidate their trips.

Speaker 2: Look, I am not denying that evaporation happens eventually. I am critiquing the timeline of that evaporation. That eutopia model you cited, it looks at the city from a macro bird’s eye view,

Speaker 1: which is how you have to evaluate citywide policy.

Speaker 2: Sure, the city average looks great on paper in 20 years, but it completely glosses over the highly localized street level air pollution spikes happening right now. Relying on a multi-decade rollout to eventually evaporate traffic while perimeter residents choke on 17% more knocks today is simply unacceptable public policy.

Speaker 1: I really think you are missing the forest for the trees here. Judging a 503 block network. By looking at three isolated pilots is like evaluating a massive plumbing system before all the pipes are connected.

Speaker 2: Okay, I see where you’re going with this.

Speaker 1: Of course, there are leaks. Leaks are entirely inevitable. When this system is incomplete, you put a blockage in one pipe, the water reroutes to the next open pipe. But full deployment is what actually forces the behavioural shift.

Speaker 2: But we don’t have full deployment, and honestly we won’t for a very long time.

Speaker 1: We are getting there. And remember, Barcelona is highly primed for this. 55% of travel in the city is already active, transport, walking, and cycling.

Speaker 2: That is true.

Speaker 1: If the city follows through with opening, say, 33 hectares of new pedestrian areas in the ice sample district alone. Drivers won’t just detour to the next street over. The friction becomes too high. The entire network becomes less hospitable to cars, so they will simply stop driving. The evaporation mechanism is completely sound. It just requires spatial scale to work.

Speaker 2: Okay. I understand the plumbing analogy. I really do, but it just don’t buy that. The physical space alone solves a density of 5,500 vehicles per square kilometre without serious collateral damage. Let me break down why To actually meet EU NO two standards across the board. Barcelona needs an overall traffic reduction of 25 to 30%. And how do we know that exact number?

Speaker 1: From the lockdowns, I assume?

Speaker 2: Exactly, because that’s the baseline drop we saw during the COVID-19 lockdowns, which was the only time the city recently came into full compliance with health standards.

Speaker 1: The lockdown was an extreme case of demand reduction.

Speaker 2: It was, but it successfully reduced demand. Physical barriers in a few neighbourhoods, or even a few dozen neighbourhoods as they build out, won’t achieve a 30% reduction fast enough to save the lungs of the people on the perimeter today.

Speaker 1: So what’s the alternative?

Speaker 2: While we build, we need coercive economic policies layered on top of this specifically, we need a congestion charge.

Speaker 1: Oh, you’re talking about the citizen proposal for a four euro weekday feed to enter the low emission zone?

Speaker 2: Yes, exactly. Because if you want traffic to evaporate, you can’t just put up a Do not enter sign on the few streets and hope the friction frustrates people enough to change their habits. You have to make the alternative. Which is driving too expensive to justify.

Speaker 1: So you think a toll is the silver bullet.

Speaker 2: The congestion charge is the heat that actually causes the evaporation. Look at Stockholm, their congestion charge resulted in a 22% traffic reduction. In its very first year. London saw a 33% reduction Pricing, not just paving, is how you solve density.

Speaker 1: It works immediately. Sure.

Speaker 2: Which is exactly what we need. We needed to prevent those adjacent street pollution spikes. The Virtual Mobility Lab warned us about

Speaker 1: pricing works in theory, but I think you are entirely ignoring the physical permanence of these policies. I am highly sceptical of relying on economic levers over architectural ones because congestion pricing is incredibly vulnerable to political cycles.

Speaker 2: Meaning what? A new mayor comes in and cancels it.

Speaker 1: Exactly. A new administration comes in and they scrap the toll. Furthermore, there’s simple habituation. Even in your own example of London, the traffic congestion rebounded over time,

Speaker 2: but rebounded somewhat. Yes.

Speaker 1: People get used to the fee, they factor it into their daily expenses, or the road space gets reallocated to delivery vehicles and the cars just come right back.

Speaker 2: That doesn’t negate the immediate massive demand reduction it provides. Right now a reduction. We desperately need to get through the transition phase,

Speaker 1: but it distracts from the permanent physical solution. I have to ask, if we rely on pricing, how do we guarantee the actual physical creation of green spaces? A four Euro toll does not plant a single tree.

Speaker 2: Fair point.

Speaker 1: A congestion charge does not lower the urban heat island effect.

Speaker 2: Wait, out of curiosity, how much does a super block actually lower the temperature

Speaker 1: by a full degree Celsius? And that happens because of the spatial reallocation. When you literally tear up the asphalt, you stop the street from absorbing solar radiation all day and baking the neighbourhood all night,

Speaker 2: right? The permeability.

Speaker 1: Yes. You put down permeable surfaces, you plant vegetation, you create canopy cover. You cannot tax the city into being green. You have to physically build it. Only an architectural transformation secures that.

Speaker 2: Okay. I am not saying we abandon the super blocks. I am not saying we don’t tear up the asphalt.

Speaker 1: It sounded like you preferred the toll.

Speaker 2: No, I am saying that placing a super block in a hyperdense traffic grid. Without a congestion charge is putting the cart before the horse. The congestion charge provides that immediate citywide traffic reduction required to prevent those horrific spikes in localized pollution on the perimeter streets while the construction happens.

Speaker 1: Okay, so you see them as complimentary.

Speaker 2: Absolutely and crucially, it funds the transformation that four Euro fee generates the immense public revenue needed to physically build out the remaining 500 super blocks you are advocating for. The architectural redesign is absolutely the destination, but the economic policy is the only safe vehicle to get us there without choking half the city in the process.

Speaker 1: I see. I think we are ultimately looking at two different time horizons. The Superblock model remains a brilliant structural re-engineering of the urban environment.

Speaker 2: It’s definitely ambitious.

Speaker 1: It is. Yes, there is transitionary friction, like the rebound effect you are concerned about, but permanently designing cars out of 45% of the city’s road space is the only way to fundamentally secure long-term urban health.

Speaker 2: It’s a huge shift.

Speaker 1: We cannot shy away from a transition. That is projected to prevent nearly 700 premature deaths every year just because the construction phase causes temporary redistribution.

Speaker 2: And my counter to that is simple. Architectural idealism cannot afford to ignore localized harm. The empirical data on the ground right now is incredibly clear,

Speaker 1: the perimeter pollution data

Speaker 2: exactly without simultaneously implementing a macroeconomic tool like a congestion charge to lower overall vehicle density. The Superblock model is just an incomplete policy. You might be permanently fixing one neighbourhood, but you’re doing it by pushing the exhaust pipe directly into the next,

Speaker 1: I think, where we absolutely converge on the sheer urgency of the status quo. The data shows that NO two concentrations caused roughly 929 premature deaths in Barcelona in 2017 alone.

Speaker 2: It’s awful.

Speaker 1: We agree that is a public health crisis of the highest order, and that single policy  approaches are likely insufficient to solve highly complex urban ecosystems.

Speaker 2: Completely agreed. The era of designing cities exclusively around the automobile is definitively over, but getting out of that century old paradigm requires us to pull every lever we have available, not just the architectural ones,

Speaker 1: right. It seems the true solution to modern urban design requires navigating both the physical space we inhabit and the economic behaviours we incentivize.

Speaker 2: For sure. There’s a lot more to explore here.

Speaker 1: We will leave it to you, the listener, to consider which lever, the architectural transformation or the economic boundary you find more vital for the future of our cities. Are we simply rerouting the arteries or do we need to fundamentally change what flows through them?

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What is the future for cities podcast?

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Episode and transcript generated with ⁠⁠Descript⁠⁠ assistance (⁠⁠affiliate link⁠⁠).