Driving–even living near traffic–makes us dumb, sick and lonely

Driving offers some compensating advantages over mass transit, of course, including a greater sense of autonomy and control. But one of the seeming conveniences of driving—that getting from home to work doesn’t force you to walk any farther than from your kitchen to your garage at one end, and from your employer’s parking lot to your desk at the other—isn’t a benefit. It’s a liability.

The big-time health benefits of walking are not a secret. More than a century ago the English historian George Macauley Trevelyan began a book titled, simply, Walking, with the line: “I have two doctors: My left leg and my right. When my body and mind are out of gear . . . I know that I shall have only to call in my two doctors to be well again.” He knew what he was talking about.

Walking 30 minutes a day—as little as a mile at each end of a daily commute, for example—lowers the risk of heart disease by up to 40%, reduces the risk of Type II diabetes by as much as 60%, and can cut the risk of stroke by a third. Osteoarthritis? Walk 30 minutes a day, and reduce your risk by 18%. Starting in the 1990s, Japan’s Osaka Company began surveying its employees in order to get a handle on the impact of lengthening the distance they walked to work, and their risk of higher blood pressure. Every additional 10 minutes spent walking to and from work was associated with a 12% reduction in hypertension.

A study at Duke University compared a brisk 30-minute walk three times a week to taking the antidepressant Zoloft. Walking worked at least as well. It’s not like this was a single outlier study, either. A group of health economists in England studied 18 years of data on more than 18,000 commuters who had been surveyed about their own mental health: whether they felt worthwhile or worthless, slept well or poorly, how well they coped with life problems. The more time they spent walking—or on public transportation—the higher their scores.

For me, though, the biggest advantage of getting around using my feet for something other than operating a car’s accelerator might be that it makes me smarter. Or, at least, less stupid. The reason is a little seahorse-shaped section of my brain—yours, too—called the hippocampus, two of which are located just under the center of the temporal lobe. The two hippocampi are critical in storing and creating memories. They’re the part of the brain first damaged by Alzheimer’s, and the one where amnesia due to oxygen deprivation occurs. Even if we avoid amnesia or dementia, though, memory gets a lot less useful the older we get, largely because the hippocampus naturally shrinks as we age.

It doesn’t have to. Though a lot of otherwise well-educated people still seem to think that a brain cell, once lost, is gone forever, this isn’t true at all. So long as you continue to produce a protein known as brain-derived neurotrophic factor, or BDNF, your brain will build new neurons and strengthen the capacity of existing ones. How to increase BDNF production? Exercise, of course.

Getting to work by foot or on my bike would make me a lot healthier, a good deal happier (or less depressed), and a little bit smarter (or less forgetful) even if I were the only one in New York doing so. There are even researchers who believe that walking, in particular, was so critical for human evolution that intelligence itself was a side effect of bipedalism. But there’s another benefit, one that has implications not just for individual commuting decisions but for a whole spectrum of transportation policies, from the way we design intersections to the speed limits we set. Choosing to drive less improves society’s mental health, too.

This is because what we see is largely determined by how we see. Driving demands tunnel vision—literally. A 2010 simulation produced by the National Association of City Transportation Officials shows that a driver’s “cone of vision” automatically excludes peripheral information, and that the faster a car travels, the more that cone narrows: moving at 30 miles per hour gives drivers less than 25% the amount of visual information that they receive at 15 miles per hour. The lack of visual context makes for snap judgments; and because drivers have to be more alert to rapidly developing dangers in a way that pedestrians aren’t, those snap judgments tend to be negative ones.

 “Can you tell me how to get to Central Park, or should I just go f&%k myself?” The good news is that, although driving makes us more suspicious, walking makes us more hopeful. I know this sounds a little odd coming from someone who lives and walks in New York, where, as the joke goes, a tourist asks for directions by saying, “Can you tell me how to get to Central Park, or should I just go f&%k myself?” But it’s true. Our sense of psychological well-being is a function of the number of positive contacts we have daily with others—not just friends and family, but strangers and neighbors. And those positive contacts are a lot more frequent outside a car.

Social cohesion and trust are improved just by living in a place with less traffic. Though the social costs of a physical environment dominated by the automobile have been debated ever since the Model T, the best (and still the most cited) study of the subject dates to the late 1960s, when Donald Appleyard, then professor of urban design at the University of California, Berkeley, performed a rigorous survey of three residential streets in San Francisco. On the surface, the streets seemed close to identical: same topography, similar demographics, and, of course, the same weather (in San Francisco, a pretty change- able thing). They differed in only one significant respect: the number of vehicles that traveled along the street on a typical weekday. On average, fewer than two thousand cars traveled down one street daily; on another, the number was eight thousand. On Appleyard’s “Heavy Street,” sixteen thousand vehicles a day. The residents of each street were then asked to complete detailed questionnaires about their respective networks of friends and acquaintances.

The results weren’t unexpected, but the degree of difference was still startling: residents on the street with the lightest traffic had, on average, three close friends living on the same block; those on the heaviest, fewer than one. The people living on the Light Street had more than twice as many acquaintances on their streets as the people living on Heavy Street. Asked to draw pictures of their blocks, they included more, and more accurate, details. When Appleyard performed follow-up interviews on his subjects, they explained why: on a heavily trafficked street, “home” meant that part of the world that was inside the doors of their houses or apartments. On the lightly trafficked ones, the concept had a very different meaning—people living there consistently referred to the entire block as “home.”

This article was adapted from Street Smart: The Rise of Cities and the Fall of Cars, by Sam Schwartz. Reprinted with permission from PublicAffairs. We welcome your comments at ideas@qz.com.

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