The number of pedestrians killed in the US each year has increased 78% since 2009:

This comes after decades of steady decline, causing many to wonder: What the hell is going on?

Brian Potter of Construction Physics recently tried to answer this question, here. Perhaps the two most common theories are that (1) bigger cars have become more popular (and bigger cars are more deadly to pedestrians), and (2) people are increasingly distracted by smartphones.

In his view, the SUV theory is maybe supportable, but the evidence is mixed. Pedestrian deaths involving smaller cars like Honda Civics are also up substantially. So it doesn’t seem to be just that.

As for the smartphone theory, Potter cites data showing that traffic accidents rarely report “distracted” driving. I call bullshit. I suspect it's because drivers don’t want to admit they were scrolling through TikTok; but even then, it doesn’t appear to be the clear cause. Smartphones are global, and yet this surge in pedestrian deaths is a uniquely American problem (based on other data from Potter).

So what is it?

My view — and this isn’t mentioned in the article — is that built form must be a factor. Much of it comes down to how we design our cities. Intuitively, this makes sense to me. But there’s also data to support it. First, if we look at pedestrian deaths per capita, there’s a clear bias toward the South and West, both of which tend to have more car-oriented urban patterns compared to the older cities in the North.

Second, if you drill down into specific urban environments — including those adopting strong Vision Zero policies — you’ll see that local trends don’t always match what we’re seeing nationally or even at the state level. For example, in recent years, cities like New York have become much safer for pedestrians:

New York City continues to defy national trends around pedestrian deaths, which are currently at a four-decade high nationwide. Traffic fatalities were down in four of the five major travel modes the DOT tracks. Compared to 2013—the last year before implementation of Vision Zero—New York City traffic deaths have dropped by 14.7%, from 299 that year. Pedestrian deaths have decreased by 35.9% compared to 2013 figures. Cyclist fatalities were also down for the third straight year (17 in 2022, down from a 20-year high of 28 in 2019), declining even as bicycle ridership has soared in recent years.

So my simple theory is this: Human-scaled spaces that are designed around pedestrians, rather than cars, are less likely to kill pedestrians.

At the same time, I do think we’ll see pedestrian deaths naturally come down in the US as autonomous vehicles become more widespread. AVs are already better — or at least safer — drivers than humans, and that will help. None of us should be driving cars anymore if you're just looking at the safety data. But I don’t see that as a good reason not to create more human-scaled spaces. They offer us much more than just safety.

Diagrams: Construction Physics

Vietnam has a building typology known as tube housing.

It is characterized by narrow building frontages, often in the range of 3 to 4 meters, and multiple skinny levels. From what I've read, tube housing first appeared in the 17th century in cities like Hanoi. Its ubiquity over the years, however, has been aided by a myriad of factors, including Vietnam's transition from capitalism to socialism. This change meant that far fewer apartment buildings were being constructed, and so households had to take matters into their own hands and build what they could.

I've also read that this building type may have something to do with the way properties were taxed based on their frontage rather than their site area, though I haven’t been able to find a reliable source for this. Whatever the case, the end result is exactly what we discussed in this recent post — The 9-Step Rule: Why Simple, Narrow Buildings Are Good for Cities. Except with these frontages, it wouldn’t even take nine steps if the average building width is closer to 3–4 meters.

What is equally interesting about this housing type is that it represents a ground-up intervention (as opposed to the result of top-down urban design) and it is highly adaptable. It is not uncommon for additional floors to be added to these tube houses as needs change, and for the ground floors to serve as garages, living rooms, thriving commercial spaces, or as all three at once. It is an entirely flexible space that fuels entrepreneurship and allows households to make money.

Just think about how much easier it would be to open your own shop if you already owned the space. Conversely, how many of these ground-floor businesses wouldn’t exist if only there were a single line in the zoning regulations that said: “Nah, sorry, you can’t start and operate your own business here.” That is what I often worry about when it comes to land-use policy: what human potential are we quashing as a result of our decisions?