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want safer streets? ditch the signs.

In an effort to increase the number (and the originality) of my posts, for the foreseeable future I’ll be focusing posts on snippets from books I have read recently which I found interesting. This post looks at the safety paradox: we are often most safe when we feel less safe. While counterintuitive, I think most recognize the logic. But how far are you willing to let it take you?

Tom Vanderbilt, from Traffic:

One study that looked at twenty-four intersections that had been converted from signals and stop signs to roundabouts found that total crashes dropped nearly 40 percent, while injury crashes dropped 76 percent and fatal crashes by about 90 percent. There is a paradox here: The system that many of us would feel is more dangerous is actually safer, while the system we think is safer is actually more dangerous. This points to a second, more subtle factor in why roundabouts are safer. Intersections of any kind are complex environments for the driver, requiring high amounts of mental workload to process things like signs, other cars, and turning movements. Drivers approaching an intersection with a green light may feel there is little left for them to do; they have the green light.

If “Slow: Children” and “Deer Crossing” signs do not seem to have noticeable effects, it hardly seems impertinent to ask, Do traffic signs work, and are they really needed at all? This question has been raised by Hans Monderman, a pioneer who was, until his death in January 2008, perhaps the world’s best-known traffic engineer. It’s probably no accident that he became famous by turning his back on decades of received wisdom in his profession and created traffic plans—like entire major intersections without lights or signs—that were radical even by the standards of his native Holland.

“The Netherlands is different,” noted Kerstin Lemke, a researcher at Germany’s Federal Highway Research Institute, as if discussing the openness toward sex and drugs in Amsterdam. “They’ve got things on the motorway we would never do.” Then again, the Netherlands has a better traffic-safety record than Germany, so maybe they’re on to something.

“Each user of a house knows that a kitchen is used differently from the bathroom,” Monderman said. “You don’t have to explain.” Why not make the difference between a village road and the rural highway that flows into it as legible?

Then came a request to do something about the traffic situation at the Laweiplein, a four-way crossing in the city of Drachten. The traffic volume was relatively high—twenty thousand cars a day, plus many scores of cyclists and pedestrians—and congestion was a growing problem. “The traffic lights were so slow,” Monderman recalled. But the challenge, as he saw it, was not just moving traffic through as quickly as possible; the Laweiplein “was also the heart of the village. It was exactly the place meant for people. But it was a horrible place, all poles and paint and fences.” Simply replacing the four-way signalized intersection with a roundabout was only half a solution. “Roundabouts work for traffic wonderfully, but in a more city-building type of way they destroy any quality of space,” Monderman said. “It’s a circular pattern, and most cities have a grid. It doesn’t fit in the space; it’s telling the wrong story.” What Monderman wanted was a traditional village square that just so happened to contain a roundabout: a “squareabout.”

After seven years of design and construction, the new Laweiplein was unveiled. It was the intersection heard around the world. Seeing it for the first time, one is immediately struck by how clean and open the space looks. Then one begins to realize why. There are no signs, no traffic lights, no zebra-striped poles, no raised curbs, none of the ugly and cheap roadside junk we have come to think is part of our “natural” world. There are simply four roads coming into a small circle at the center of a large square. The space is dominated not by the roads but by sidewalks and a series of fountains whose water gushes higher as more traffic enters the crossing.

What was going on? Apparently, the drivers were not using the road markings but were using their brains—and the results, far from chaos, seemed to indicate more order. What white lines do is enable drivers to drive faster and, intentionally or not, closer together. Similarly, several studies in different countries have found that drivers tend to give cyclists more space as they pass when they are on a street without a bicycle lane. The white marking seems to work as a subliminal signal to drivers that they need to act less cautiously—that it’s the edge of the lane, and not the cyclist, they need to worry about.

While this idea has been around in one form or another since the early days of the automobile—indeed, it was used to argue against railroad safety improvements—it was most famously, and controversially, raised in a 1976 article by Sam Peltzman, an economist at the University of Chicago. Describing what has since become known as the “Peltzman effect,” he argued that despite the fact that a host of new safety technologies—most notably, the seat belt—had become legally required in new cars, the roads were no safer. “Auto safety regulation,” he concluded, “has not affected the highway death rate.” Drivers, he contended, were trading a decrease in accident risk with an increase in “driving intensity.” Even if the occupants of cars themselves were safer, he maintained, the increase in car safety had been “offset” by an increase in the fatality rate of people who did not benefit from the safety features—pedestrians, bicyclists, and motorcyclists. As drivers felt safer, everyone else had reason to feel less safe.


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