Ideas

Why Driverless Cars May Make Cities Sprawl Even More

April 20, 2016

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A Google self-driving car. Photo © Grendelkhan / Wikimedia through a Creative Commons license
A Google self-driving car. Photo © Grendelkhan / Wikimedia through a Creative Commons license

You’ve seen the news: more cars are now driving themselves. Even non-luxury cars like the Honda Civic and Ford Fiesta now feature autonomous braking systems, and other cars contain autonomous cruise control.

Most ambitiously, Google and other companies have been working on testing truly driverless cars, where a computer has full control of moving the vehicle. The Google self-driving car has an amazingly good safety record: after more than 1.3 million miles, it has had less than 20 accidents, orders of magnitude safer than most human drivers. There is a sense in the automotive industry that driverless cars will arrive on the marketplace, sooner or later.

Certainly most people recognize the safety gains of technological advances like autonomous braking. But the media hype around truly driverless cars tends to be rapturous and utopian. Some writers have seen the driverless car as the end to looking for on-street parking in cites, since the car could go park itself. Or maybe, some writers hope, the driverless car will accelerate the trend from car ownership to car and ride sharing (e.g., ZipCar, Uber, Lyft).

But from my research into urban planning and sustainability, I have become convinced there is a potential downside to the driverless car. What if driverless cars, far from being a technology that reduces the dependence of our society on cars, actually increases it? Environmentalists have been pushing for the last few decades for a vision of walkable, denser, hip cities. This is good for the planet (less greenhouse gas emissions, less sprawl) and good for us (more walking and biking leads to less obesity). What if the driverless car takes us away from the vision, toward more sprawl?

Urban historians have learned that over centuries, the amount of time spent traveling by people in cities has been relatively constant. In a medieval city, people walked everywhere, and so most people’s daily routine took them at most only about 3-4 kilometers from their home, perhaps an hour walk.

The increase in horse-drawn carriages over the 18th and 19th centuries made longer distance travel possible, while the rise of street cars in the 19th and early 20th centuries led to new neighborhoods at a lower density that were farther from the urban core. This, of course, was followed by the era of mass car ownership; highways dramatically increased the distances we can travel. Over all those technological changes, though, the amount of time we spent commuting didn’t change much. For most people, a commute of more than an hour one way starts to feel onerous.

Cities develop in a pattern and at a density that is a result of this fundamental tradeoff. Life in the center city is often expensive, loud, and dirty, and the suburbs or edges of a city may seem cheaper (at least in terms of the cost per square meter of housing) and greener.

In the U.S., there are other advantages to the suburbs; the schools are often better and the municipal governments are sometimes more functional. But people’s time is finite, so living far out from the city has its limits. Based on their preferences, people choose some point along this tradeoff from center city to suburb, and the aggregate preferences of lots of people determine how dense or sprawled out our cities are.

Antioch from above. Photo © Shawn Clover / Flickr through a Creative Commons license
Antioch from above. Photo © Shawn Clover / Flickr through a Creative Commons license

Driverless cars, if they were truly autonomous, would begin to alter this equation. The time in the car could be spent for something pleasurable like reading a good book (indeed, that is one of the things I love about commuting by metro in Washington, DC). Or for workers whose white collar job involves sending emails or calling in to phone meetings or editing documents on a computer, the time in the car could become part of their work day.

The Internet hasn’t stopped these workers from needing to meet face to face, occasionally. There is a lot of evidence that the Internet didn’t let people entirely leave urban areas, since they need to be close enough to make it into the office sometimes. But how many more white-collar workers will be willing to accept a longer commute once they realize that time in the car can be productive time, rather than a soul-sucking commute?

Driverless cars may free a fraction of workers to live farther out, where land is cheaper. They’d be willing to “drive” more miles on average. Seen in its historical perspective, the Google car is not a revolutionary technological change, but part of a century-long shift toward people travelling on average more kilometers a day.

A lot has been written about millennials and their desire to live in cities, to reject the rather staid life in a car-centric suburb for a more active, walkable life in an urban center. Indeed, my family in a way is at the front end of that wave — we have chosen to live in Washington, DC, within walking distance to a subway, rather than farther out in the suburbs.

But there are still tradeoffs — we live in a small apartment rather than a stand-alone house, and while the schools are improving in DC they are still not as good as the richer suburbs. Even a change in average preferences of a generation, like millennials, doesn’t erase this fundamental tradeoff of city life.

A Google self-driving car. Photo © LoKan Sardari / Flickr through a Creative Commons license
A Google self-driving car. Photo © LoKan Sardari / Flickr through a Creative Commons license

As the millennials hit the age of having children and starting families some fraction of them will choose the suburbs. And a driverless car makes the increased travel time of the suburbs less daunting, perhaps even hip and cool.

Driverless cars, by making driving more pleasant, may increase how much we drive. How should the environmental community respond to this?

We can’t be reflexively against cars and driving, as that is a niche position that is pretty separated from the reality of most Americans, who often drive as their main mode of transit. In my opinion, we need to focus on solving the problems we really care about, rather than bemoaning increased driving per se.

Increased vehicle miles travelled due to driverless cars might increase greenhouse gas emissions, unless the cars of the future are also low or zero-emission vehicles, a very achievable technological goal given some of the technologies already on the market.

Increased driving will lead to a push to develop suburbs further out, and a push to build more roads, and the environmental community will have to be ready to talk about how those new settlements should be built, making sure roads and developments avoid environmentally-sensitive areas.

And for those who are passionate about creating walkable, vibrant urban neighborhoods, they will still need to work to create and steward those places. The driverless car won’t change these goals of the environmental community, but it will change how our cities are structured, in perhaps significant ways.

Get ready.

Rob McDonald

Dr. Robert McDonald is Lead Scientist for the Global Cities program at The Nature Conservancy. He researches the impact and dependences of cities on the natural world, and help direct the science behind much of the Conservancy’s urban conservation work. More from Rob

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2 comments

  1. It is time to start zoning a (or another) band of green space around our cities. Driverless cars are coming, but we can control their impact. It makes a difference whether your driverless car takes you to the central city or to a commuter rail station.

  2. This is a troubling concept, however there are housing affordability issues in most cities that can be counteracted with densification of suburbs within a reasonable distance using accessible transportation. The fee system/economics of the system will be of critical importance, determining if we will make a system that fosters equity through transit access or the opposite.