Traffic: Why We Drive the Way We Do (and What It Says About Us) - Tom Vanderbilt (2008)

Chapter 7. When Dangerous Roads Are Safer

The Highway Conundrum: 
How Drivers Adapt to the Road They See

An overturned cart is a warning to oncoming drivers.

—Chinese proverb

Just before dawn on Sunday, September 3, 1967, there was an unusually festive air in the streets of Stockholm. Cars honked, passersby cheered, people gave flowers to police officers, pretty girls smiled from the curb. The streets were clogged with cars, many of which had been waiting for hours to participate in a historic traffic jam. People stole bicycles simply to be a part of traffic. At the moment the bells chimed for six o’clock, Swedes began driving on the right.

It had taken years of debate, and much preparation, to get to this point. Motions to switch from left-side driving had been raised in Parliament several times in previous decades, only to be shot down. The issue was put before Swedes in a 1955 referendum, but the measure was overwhelmingly defeated. Undeterred, backers of right-side driving finally got a measure approved by the government in 1963.

Proponents said that driving on the right, as was the practice in the rest of Scandinavia and the bulk of Europe, would lower the number of accidents in which foreigners were increasingly becoming involved. Most cars in use already had steering wheels on the left side. Those opposed, which was most of Sweden, grumbled about the huge costs of the changeover, and said that accident rates were bound to rise.

As “H-Day” (after höger, the Swedish word for “right”) approached, the predictions of ensuing chaos and destruction grew dire. “What is going to happen here in September has cast many grotesque shadows all over Sweden,” the New York Times observed darkly. This despite four years of preparation and an especially energetic blitz of public-service announcements in the final year before the changeover. There was even a pop song, titled “Håll dej till Höger, Svensson!” or “Let’s All Drive on the Right, Svensson!” (after a stereotypically common Swedish surname).

And what happened when Swedes started driving on the other side of the road, many for the first time in their lives? The roads got safer. On the Monday after the change, the traffic commissioner reported a below-average number of accidents. True, this may have been anticipated, despite the gloomy predictions. For one, many Swedes, scared witless of the spectacle, undoubtedly chose not to drive, or drove less. For another, a special speed limit, which had already been in place for some months before the changeover, was enforced: 40 kilometers per hour in towns, 60 on open roads, 90 on highways. Lastly, the whole operation was run with Scandinavian efficiency and respect for the law. This was the country that gave the world Volvo, by God—how could it not be safe?

Remarkably, it was not just for a few days, or even weeks, after the changeover that Sweden’s roads were safer. It took a year before the accident rate returned to what it had been the year before the changeover. This raises the question of whether the changeover actually achieved anything in the long run for safety, but in the short term, when one might have predicted an increase in accidents as an entire nation went through the learning curve of right-hand driving, Sweden actually became safer. Faced with roads that had overnight theoretically become more dangerous, Swedes were behaving differently. Studies of drivers showed they were less likely to overtake another when a car was approaching in the oncoming lane, while pedestrians were looking for longer gaps in the traffic before choosing to cross.

Had Sweden’s roads actually become more dangerous? They were the same roads, after all, even if drivers were driving on a new side. What had changed was that the roads felt less safe to Swedish drivers, and they seemed to react with more caution.

Most people have probably had similar moments. Think about a roundabout, quite common in Europe but still rare to these shores. For many Americans they are frightening places, their intimidation factor perhaps best captured by the plight of the hapless Griswold clan in National Lampoon’s European Vacation, who, having entered a London traffic circle, find that they cannot leave. They orbit endlessly, locked in a traffic purgatory, until night closes in, the family has fallen asleep, and the father is babbling uncontrollably. Whether this rings true or not, it must be pointed out that the much-maligned traffic circle is not the same thing as a roundabout. A traffic circle varies in a number of ways, most notably in that cars already in the circle must often yield to cars entering the circle. Traffic circles are also larger, and cars enter at a much higher speed, which makes for less efficient merging. They may also rely on traffic signals. In roundabouts, which are free of signals, cars entering must yield to those already in the circle. We have already seen that roundabouts can be more efficient, but it may surprise you to learn that modern roundabouts are also much safer than a conventional intersection with traffic lights.

The first reason has to do with their design. Intersections are crash magnets—in the United States, 50 percent of all road crashes occur at intersections. At a four-way intersection, there are a staggering fifty-six potential points of what engineers call “conflict,” or the chance for you to run into someone—thirty-two of these are places where vehicles can hit vehicles, and twenty-four are spots where vehicles can hit pedestrians.

Roundabouts sharply drop the total number of potential conflicts to sixteen, and, thanks to their central islands (which create what engineers call “deflection”), they eliminate entirely the two most dangerous moves in an intersection: crossing directly through the intersection, often at high speed (the average speed in most roundabouts is half that of conventional intersections, which increases safety for surrounding pedestrians), and making a left turn. This little action involves finding a suitable gap in oncoming traffic—often as one’s view is blocked by an oncoming car waiting to make its own left turn—and then, as your attention may still be divided, making sure you do not hit a pedestrian in the crosswalk you are entering as you whisk through your turn. 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. But traffic lights have pernicious effects in and of themselves, as Kenneth Todd, a retired engineer in Washington, D.C., has pointed out. The desire to “catch” a green makes drivers speed up at precisely the moment they should be looking for vehicles making oncoming turns or entering the main road from a right turn on red. The high placement of traffic lights also puts drivers’ eyes upward, away from the street and things like the brake lights of the slowing cars they are about to hit. Then there are the color-blind drivers who cannot make out the red versus green, and the moments when sunlight washes out the light for everyone.

With a roundabout, only a fool would blindly sail into the scrum at full speed. Drivers must adjust their speed, scan for openings, negotiate the merge. This requires more workload, which increases stress, which heightens the feeling of danger. This is not in itself a bad thing, because intersections are, after all, dangerous places. The system that makes us more aware of this is actually the safer one.

Once, on a driving trip in rural Spain, I decided to take a shortcut. On the map, it looked like a good idea. The road turned out to be a climbing, twisting, broken-asphalt nightmare of blind hairpin turns. There were few guardrails, just vertigo-inducing drops into distant gulleys. The few signs there were told me what I already knew: PELIGRO. Danger. And how did I drive? Incredibly slowly, with both hands locked on the wheel, eyes boring straight ahead. I honked ahead of every blind curve. My wife, who fears both heights and head-on collisions, never trusted me with a Spanish map again.

Was the road dangerous or safe? On the one hand, it was incredibly dangerous. The “sight distances,” as road engineers call the span required for one to see a problem and safely react to it (based on a certain travel speed), were terrible. The lanes were narrow and not always marked. There was only the occasional warning sign. Had there been a collision, there was little to keep me from tumbling off the edge of the road. And so I drove as if my life depended on it. Now picture another road in Spain, the nice four-lane highway we took from the airport down to Extremadura. There was little traffic, no police, and I was eager to get to our hotel. I drove at a healthy pace, because it felt safe: a smooth, flat road with gentle curves and plenty of visibility. The sun was shining; signs alerted me to every possible danger. And what happened? Grown briefly tired from the monotony of the highway (drivers have a greater chance of becoming drowsy on roads with less traffic and on divided highways free of junctions) and the glare of the sun, I just about fell asleep and ran off the road. Was this road dangerous or safe?

Of the two roads, the highway was of course the more objectively safe. It is well known that limited-access highways are among the safest roads we travel. There is little chance of a head-on collision, cars move at relatively the same speeds, medians divide opposing traffic streams, curves are tamed and banked with superelevation to correct drivers’ mistakes, there are no bikes or pedestrians to scan for, and even if I had started to nod off I would have been snapped back to attention with a “sonic nap alert pattern,” or what you might call a rumble strip. At the worst extreme, a guardrail may have kept me from running off the road or across the median, and if it was one of the high-tension cable guardrails, like the Brifen wire-rope safety fence, increasingly showing up from England to Oklahoma, it might have even kept me from bouncing back into traffic.

Those rumble strips are an element of what has been called the “forgiving road.” The idea is that roads should be designed with the thought that people will make a mistake. “When that happens it shouldn’t carry a death sentence,” as John Dawson, the head of the European Road Assessment Programme, explained it to me. “You wouldn’t allow it in a factory, you wouldn’t allow it in the air, you wouldn’t allow it with products. We do allow it on the roads.”

This struck me as a good and fair idea, and yet something nagged at the back of my brain: I couldn’t help but think that of the two roads, it was the safer one on which I had almost met my end. Lulled by safety, I’d acted more dangerously. This may seem like a simple, even intuitive idea, but it is actually an incredibly controversial one—in fact, heretical to some. For years, economists, psychologists, road-safety experts, and others have presented variations on this theory, under banners ranging from “the Peltzman effect” and “risk homeostasis,” to “risk compensation” and the “offset hypothesis.” What they are all saying, to crudely lump all of them together, is that we change our behavior in response to perceived risk (an idea I will explore more fully in Chapter 9), without even being aware that we are doing so.

As my experience with the two roads in Spain suggested, the question is a lot more subtle and complicated than merely “Is this a dangerous or safe road?” Roads are also what we make of them. This fact is on the minds of engineers with the Federal Highway Administration’s Turner-Fairbank Highway Research Center, located in Langley, Virginia, just next to the Central Intelligence Agency.

The first thing to think about is, What is a road telling you, and how? The mountain road in Spain did not need speed-limit signs, because it was plainly evident that going fast was not a good idea. This is an extreme version of what has been called a “self-explaining road,” one that announces its own level of risk to drivers, without the need for excessive advice. But, you protest, would it not have been better for that mountain road to have signs warning of the curves or reflector posts guiding the way? Perhaps, but consider the results of a study in Finland that found that adding reflector posts to a curved road resulted in higher speeds and more accidents than when there were no posts. Other studies have found that drivers tend to go faster when a curve is marked with an advisory speed limit than when it is not.

The truth is that the road itself tells us far more than signs do. “If you build a road that’s wide, has a lot of sight distance, has a large median, large shoulders, and the driver feels safe, they’re going to go fast,” says Tom Granda, a psychologist employed by the Federal Highway Administration (FHWA). “It doesn’t matter what speed limit or sign you have. In fact, the engineers who built that road seduced the driver to go that fast.”

But those same means of seduction—the wide roads, the generous lane widths, the capacious sight distances, the large medians and shoulders—are the same things that are theoretically meant to ensure the driver’s safety. This is akin to giving a lot of low-fat ice cream and cookies to someone trying to lose weight. The driver, like the would-be dieter, is wont to “consume” the supposed health benefits. Consider a key concept in traffic safety engineering: the “design speed” of roads. This is a confusing concept, not least because engineers are often not so good at explaining their concepts to nonengineers. The so-called Green Book, the bible of U.S. highway engineers, defines “design speed” as the following: “The maximum safe speed that can be maintained over a specified section of highway when conditions are so favorable that the design features of the highway govern.” Got that? No? don’t worry—it confuses traffic people too. An easier way to understand design speed is to think of the speed that most people—what engineers refer to as the “85th percentile” of drivers—generally like to travel (thus leaving out the suicidal speeders and stubborn slowpokes). As we saw in the previous chapters, leaving it up to drivers to figure out a safe speed is itself risky business.

Even more confusingly, sometimes this speed matches the speed limit, and sometimes it does not. Once engineers figure out the 85th percentile speed, they try to bring, where possible, the various features of the highway (e.g., the shoulders, the curves, the “clear zones” on the side of the road) into line with that speed. So does this mean that everyone then travels at the “safe” design speed? Not exactly. As Ray Krammes, the technical director of the FHWA’s Office for Safety Research and Development, explained to me, drivers routinely exceed the design speed. “We know we can drive faster than the design speed,” he said. “We’re doing it every day. We set a design speed of sixty and people are driving seventy. If it’s a seventy-miles-per-hour design, there are a number of people out there pushing seventy-five or eighty miles per hour.” Drivers, in effect, are every day loading twenty-one people on an elevator that has a capacity of twenty and hoping that there’s just that extra margin of safety left.

As we have seen, traffic engineers face a peculiar and rather daunting task: dealing with humans. When structural engineers build a bridge, no one has to think about how the stress factors and loads of the bridge will affect the behavior of the wind or water. The wind or water will not take a safer bridge as an invitation to blow or flow harder. It’s a different story when engineers design a road. “When the engineers build something,” Granda says, “the question everybody should ask is, What effect will it have on the driver? How will the driver react, not only today, but after the driver sees that sign or lane marking over a period of time? Will they adapt to it?”

To try to answer these questions, Granda, who works in the Human Centered Systems Laboratory at FHWA, spends his days running drivers on test roads in the agency’s driving simulator. “It is hard to know how human beings will react,” he notes. “We can decide to do something, and we think we know how they’re going to react. You don’t really know.” As Bill Prosser, a veteran highway designer for the agency, described it to me, “there are three things out there that affect the way a highway operates: the design, the vehicle, and the driver. We as design engineers can only control one of those. We can’t control the driver, whether they’re good, bad, or indifferent.”

The best thing engineers can do, the thinking has gone, is make it easy. “You can’t violate driver expectation,” says Granda. Tests of what researchers call “expectancy” routinely show that it takes drivers longer to respond to something they do not expect than something they do expect. Think of the mental models described in Chaper 1: People were faster to respond when character traits corresponded to names in a way they expected (“strong John” versus “strong Jane”). Similar things happen in traffic. It takes us longer to process the fact that a car is approaching in our lane on a two-lane highway, instead of, as we would expect, in the other lane. A driver in Maine will brake faster for a moose than for a penguin. As David Shinar, a traffic researcher in Israel, has described it, “That ‘second look’ that we colloquially say we take when ‘we can’t believe our eyes’ may be a very real and time-consuming effort.”

This is expressed on the highway in all kinds of subtle ways. Highway engineers have long known that a set of curves, seemingly a dangerous road segment, is less dangerous than a curve that comes after a long stretch of straight highway. A similar principle exists in baseball: A batter can more easily hit a curveball if he sees nothing but curveballs than when he is thrown a curveball after a steady diet of fastballs. So engineers strive for what they call “design consistency,” which basically means: Tell drivers what to expect, and then give it to them.

The flip side of this is that too much expectancy can be boring. You might feel, for instance, that interchanges, where the on-ramps and off-ramps swirl into the highway, are the most dangerous areas on the highway. They are certainly the most stressful, and they are home to the most crashes. But that’s not where most people lose their lives. “In terms of fatalities,” says Michael Trentacoste, the director of the Turner-Fairbank center, “the highest number is ‘single-vehicle run-off road.’” I thought back to my near accident in Spain. “If you look at Wyoming,” he continues, “they have a tremendous amount of single-vehicle run-off-the-road accidents. A few years ago they had the highest percentage of run-off-the-road [accidents] on the interstate. You’ve got long stretches, a lot of nighttime driving, people falling asleep.”

This is why road designers will often introduce subtle curvatures, even when it is not warranted by the landscape. One rough rule of thumb for highways is that drivers should not drive for more than a minute without having a bit of curve. But highway curves, most of which can be driven much like any other section, are often not enough to keep a tired driver awake. Which is why engineers, starting in the 1980s, began to turn to roadside rumble strips. The results were striking. After they were installed on the Pennsylvania Turnpike, run-off-road crashes dropped 70 percent in the period studied.

Those rumble strips would hardly lull drivers into falling asleep, knowing they’ll be startled awake if they drifted off the road. But does something about the highway itself help drivers fall asleep in the first place? The line between safety and danger is not always well defined, nor is it always easy to locate.

When the U.S. Interstate Highway System was first built, engineers could not know what to expect once everyone got on the highway at the same time. “We never did have a cookbook when we started building the Interstate,” the FHWA’s Prosser told me. Engineers are still learning what works and what does not. Exiting on the left on interstate highways, a fixture in “the early days,” has been phased out wherever possible—partially because its rarity makes us slower to react. Another fixture, the cloverleaf interchange, so named because its four looping ramps look like a clover from above, has also fallen out of favor. “When we started building interstates they were pretty much the interchange of choice,” said Prosser. Cloverleafs were originally a brilliant, space-saving solution to a major problem: how to get traffic to flow across to two interconnecting roads without stopping. This made them useful for joining two intersecting highways (they are also quite good at preventing people from entering the freeway in the wrong direction of travel, an act that is said to be responsible for 350 deaths per year in the United States alone).

But they have one big drawback: The on-ramp loop enters the highway just beyond where cars are exiting via the off-ramp loop. The two streams must mix. Engineers call this the “weaving section,” a mysterious, traffic-tossed tempest full of what engineers call “turbulence” and “friction,” in which people coming onto and getting off the highway end up in each other’s way. Drivers at different speeds, scanning for directional signs, have to probe openings (i.e. make “gap acceptance” decisions) and sometimes get across several lanes—often quite suddenly. Interchanges, as it happens, are where most crashes on freeways occur—according to studies, the shorter the weave section, the higher the crash rate. With light traffic, the cloverleaf presents less of a problem, but when “weaving volume” on the two loops tops the magic number of one thousand vehicles per hour (hardly a rarity these days), things begin to break down. Because of the curious nonlinear dynamics of traffic, when traffic volume doubles, the length of weaving section required to keep it moving smoothly triples. Over time, engineers have responded by moving the weaving section out of the main highway flow and onto special “collector” lanes, which, where possible, seems to be safer and more efficient.

Highways are continuing to evolve. Recently, as traffic volumes have grown, and with new highway building increasingly unaffordable or undesirable, some agencies have begun adding new lanes to highways by either eliminating the shoulder lane or making the existing lanes narrower. In theory, this is riskier because on narrow lanes there is a greater chance of one car drifting into another. There is literally less room for error. On the other hand, wider lanes, which are presumably safer, have been shown to increase speed and may encourage drivers to drive less cautiously. Indeed, some reports have even suggested that lanes wider than the typical U.S. twelve-foot standard may actually be less safe. So far, studies that have looked into the narrowing of highway lanes have come to mixed conclusions on whether the new layouts are more or less safe. In some cases, the difference was not statistically significant. This suggests that the way drivers behave is as important as the way a road is designed. As Ezra Hauer, a Canadian engineer and traffic-safety expert, once put it, “Drivers adapt to the road they see.”

There is a simple mantra you can carry about with you in traffic: When a situation feels dangerous to you, it’s probably more safe than you know; when a situation feels safe, that is precisely when you should feel on guard. Most crashes, after all, happen on dry roads, on clear, sunny days, to sober drivers.

The Trouble with Traffic Signs—and How Getting Rid of Them Can Make Things Better for Everyone

Try to remember the last time you saw, while driving, a “School Zone” or “Children at Play” sign. Chances are you will not remember, but if you can, now try to recall what you did when you saw it. Did you suddenly slow? Did you scan for children? If you’re like most people, you did nothing. You may not have understood what it was asking you to do, which is rather common—in one study, subjects who were shown a sign warning, WATCH FOR FALLEN ROCKS,were split equally between those who said they would look for rocks falling at the moment and speed up and those who said they would slow down and look for rocks already on the road. Perhaps signs should simply say, WATCH FOR ALL ROCKS, EVERYWHERE.

More likely, the reason you did nothing when you saw the sign is that there were no children playing. If there were children playing, you probably saw them before you saw the sign. “Children at Play” signs have not been shown to reduce speeds or accidents, and most traffic departments will not put them up. Yet why do we seem to see so many? City governments usually post them to assuage complaints by neighborhood residents that people are speeding down their streets. They may have even been put up after a child was hit or killed by a driver, in which case it would probably be more effective to erect a sign saying just that.

Similarly, drivers routinely see signs warning of deer crossings (in the United States) or elephant crossings (in Sri Lanka) or camel crossings (in Tunisia). It is difficult to say what’s going on in the mind of a driver when he or she sees a deer or elephant or camel crossing sign, but studies have shown that most drivers do not change their speed at all. A Colorado trial featured a special animated deer sign (no, it wasn’t Bambi). Researchers presumed that the animated sign would draw more attention and heighten driver awareness. For a few weeks, it was turned away from the road, then turned back. There were actually more deer killed when the sign was activated than when it was not, even though fewer deer had crossed. The researchers then went so far as to place a deer carcass next to the animated sign—only then did drivers finally slow.

Traffic engineers have tried putting signs up only during migratory seasons or using special flashing signs equipped with sensors to detect the presence of deer, but these so-called dynamic signs are not only costly but prone to false alarms and maintenance issues, not to mention being riddled with buckshot, particularly in parts of rural America. (Maybe in the off-season deer hunters practice on deer signs.) Researchers in Wyoming who put up a special deer-sensing, flashing system were able to get some drivers to slow down when they included a deer decoy, but they walked away with the opinion that “these reductions in vehicle speed would most likely not reduce the probability of a deer-vehicle collision.” Maybe deer should simply be dressed in head-to-toe blaze orange outfits, like the people hunting them!

Perhaps the most absurd warning-sign case involved moose advisories in Newfoundland. One foggy stretch of road was home to not only many car-moose collisions but many collisions between cars and cars stopping to take pictures of moose. And so signs were erected that featured full-size, reflective silhouettes of moose. Unfortunately, tourists found these pretty interesting too, and as they slowed or stopped to take photos, the moose signs themselves became crash hot spots. The next logical step? Create new signs that read CAUTION: MOOSE SIGNS AHEAD.

Many traffic signs have become like placebos, giving false comfort to the afflicted, or simple boilerplate to ward off lawsuits, the roadway version of the Kellogg’s Pop-Tarts box that says, “Warning: Pastry Filling May Be Hot When Heated.” Engineers insist that they are necessary to protect municipalities from liability lawsuits.

But what is a sign actually telling a driver? As Carl Andersen of the FHWA pointed out during my visit, the same sign can mean two different things in two different places. Take the chevron warning sign, the one that looks like a mathematical “greater or less than” symbol. “You drive in Vermont and you see a chevron sign, you better start braking for that curve,” Andersen said. “You see that chevron in Connecticut, you better ignore it. They pick different rates of curvature to put these chevron signs up to provide that kind of warning. So even though there’s guidelines to do it consistently, there’s enough leeway in there that they do it at different times.” Nor does a sign always mean the same thing: “Bridge Freezes Before Roadway” does not tell the driver whether the bridge is frozen, and in July it tells the driver absolutely nothing. Should a “65 MPH” speed-limit sign say something else when it’s raining? Engineers have created costly dynamic signs in response to all of these issues, but the real question may be, At what point must common sense do the work of a sign?

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.

If people have heard of Monderman, they tend to recall something about “the guy in the Netherlands who hated traffic signs.” But there is, in fact, one traffic sign that Monderman loved. It stands at the border of the small village of Makkinga, in Friesland. It announces a 30 kilometers per hour speed limit. Then it says, WELKOM. Finally, it says: VERKEERSBORDVRIJ!! In English this means, roughly, “Free of traffic signs.”

A traffic sign announcing the lack of traffic signs is a good joke, but it’s also a perfect symbol of Monderman’s philosophy. The sign itself is superfluous, for a driver can see that there are no traffic signs in Makkinga. After all, Monderman pointed out, what do traffic signs actually tell us? One day, driving through Friesland in his Volvo, Monderman gestured toward a sign, just before a bridge, that showed a symbol of a bridge. “Do you really think that no one would perceive there is a bridge over there?” he asked. “Why explain it? How foolish are we in always telling people how to behave. When you treat people like idiots, they’ll behave like that.”

Monderman’s work was far more complex than a simple dislike of traffic signs. It revolved around a central theory that said there are two kinds of space: The “traffic world” and the “social world.” The traffic world is best exemplified by the highway. This world is impersonal, standardized, meant only for cars. It is all about speed and efficiency and homogeneity. Monderman, a great fan of the German autobahn, happened to like this world. The social world, on the other hand, is seen in a place like a small Dutch village. These are places where the car is meant to be a guest, not the sole inhabitant. The street has other uses beyond being a means for people to drive quickly from one place to another. Behavior is governed by local customs and interpersonal contact more than abstract rules. Monderman liked this world too, but he did not want it to have anything in common with the German autobahn.

Yet the traffic engineers, argued Monderman, with their standardized signs and markings, have forced the traffic world upon the social world. “When you built a street in the past in our villages, you could read the street in the village as a good book,” he said. “It was as readable as a book. Here is the entrance to the village, over there is a school, maybe you can shop in that shop over there. There’s a big farmyard and perhaps there’s a tractor coming out. Then the traffic engineers came and they changed it into an absolute uniform piece of space.” Drivers, he maintained, are no longer taking cues from the social life of the village; they’re working off the signs, which have become such a part of our world that “we don’t see them anymore.” Suddenly, the village’s main road is just another segment of the highway passing through, with only a few small signs to tell anyone otherwise. This may be why speeding tickets are so common at the entrances to small towns all over the world. Rather than the simple greed of the local municipality, it is also that the road through the village so often feels the same as the road outside the village—the same width, the same shoulders. The speed limit has suddenly been cut in half, but the driver feels as if he or she is still driving the same road. That speeding ticket is cognitive dissonance.

In the mid-1980s, Monderman had an epiphany that is still reverberating throughout the world. He was called in to rework the main street of a village called Oudehaske. Villagers, as they do the world over, were complaining about cars speeding through the village, on a wide asphalt road with steady traffic volumes. Before Oudehaske, Monderman’s response, like that of any good Dutch traffic engineer, had been to deploy the arsenal of what is known as “traffic calming.”

Traffic calming is, essentially, the art of getting drivers to slow down. You have traveled down a street on which traffic-calming measures have been applied, even if you were not aware of the taxonomy of devices. The most famous is the speed bump, the steep, jarring obstruction that dates to the dawn of the car itself. With the exception of places like Mexico City, speed bumps are mostly restricted to school parking lots and the like. What you see on streets nowadays is the “speed hump,” a wider, more gently sloping creature that, among other things, helps cities avoid lawsuits from car owners with ruined suspensions. There are a veritable Audubon guide’s worth of different hump styles, from “parabolic” to “sinusoidal” to the popular English import known as the “Watts profile.” A really wide hump with a flat plateau is called a “speed table.” Apart from these myriad undulations, there are also “chicanes,” which sound like French cigarettes but are really little S-shaped artificial curves that drivers must slow to navigate. “Neck-downs” (a.k.a. “bulb-outs,” “nubs,” or “knuckles”), meanwhile, are small extensions added to curbs to make intersections narrower, meant to induce drivers to slow and, at the very least, give pedestrians a shorter—and thus safer—distance to cross.

The list goes on—which should give you an idea of how hard it is to calm traffic—with any number of “diagonal diverters,” “median chokers,” and “forced-turn islands” (also called “pork chops,” for their shape). If you want to sound smart around your friends, just remember that engineers refer to bumps and the like as “vertical deflection,” while anything that relies on squeezing and narrowing is “horizontal deflection.”

Traffic-calming devices have been shown to slow speeds and reduce the volume of through traffic. But as with any medicine, the right drug—and the right dosage—must be administered. Many people think that stop signs are a good way to calm speeds in neighborhoods. One problem is that the power of these signs diminishes with use: The more stop signs, the more likely drivers are to violate them. Studies have also shown that stop signs do little if anything to reduce speed—drivers simply go faster at the midblock location to make up time. This issue plagues speed humps too, which is why engineers advise placing them no more than three hundred feet apart, so drivers do not have time to speed. As with any drug, there are side effects: Slowing and accelerating for humps increases noise and emissions, while studies have suggested that speed humps on one block can lead to higher speeds or more traffic on another. People opposed to traffic-calming measures have argued that they delay emergency responders, but researchers in Portland, Oregon, found that they added ten seconds at most to these trips—no more than any other random delay. Would you want to live on a neighborhood street that made the rare fire-truck visit ten seconds faster but was also a safe haven for faster, noisier, and more dangerous traffic every day?

As it happens, many of these traffic-calming innovations were first popularized in the Netherlands. In the beginning, they were almost impromptu acts, a kind of radical street theater directed against the growing encroachment of cars in the city. Joost Váhl, a progressive engineer working for the city of Delft in the late 1960s, was one of their key architects. Sitting one afternoon in his tidy house in Culemborg, Váhl recalled a series of outlandish stunts that ranged from a “dial-a-bump” service (citizens could call and request “bumps” in front of their homes), to the staging of a bicycle accident (“we wanted to know if car drivers would stop and help or pass us by”), to putting up false construction sites on city streets (“we found out that when streets are broken up for repair, everything is functioning perfectly with half of the space”). These tactics, which were really investigations into how to get cars and people to coexist in cities, eventually made their way into genuine social institutions. The most famous of these were the woonerven—the word translates roughly into “living yards”—which began to spring up in European cities in the early 1970s.

For decades, planners had said that people and traffic should be segregated, with cars on speedy urban motorways and pedestrians shuttling around on elevated networks of bridges and walkways. Many saw this as a capitulation of the city to the car, while as early an observer as Charles Dickens understood the futility in trying to get pedestrians to ascend pedestrian bridges when people preferred to simply cross at street level. (“Most people would prefer to face the danger of the street,” he wrote, “rather than the fatigue of getting upstairs.”)

The woonerven reversed this idea, suggesting that it was people who lived in cities and that cars were merely guests. Neighborhood streets were “rooms” to be driven through, at no higher than walking speeds of 5 to 10 miles per hour, with drivers being mindful of the furniture and decor—not just speed humps but benches, flowerpots, and nice cobble-stones—and, more important, the residents. Even today, woonerven plans seem radical, with children’s sandboxes sitting cheek-by-jowl to the street and trees planted in the middle of traffic. The reports that trickled in, however, talked about how children were playing outside longer, often without supervision. In time, the woonervengot their own traffic signs (a small icon of a house with a child standing next to it). These were marks of the concept’s success, but in the eyes of Monderman, those signs also rather defeated the purpose: Drive carefully near the woonerven, the sign implies, but drive less carefully everywhere else.

By the time Monderman had been called to rework the village of Oudehaske, the political winds of traffic planning had shifted, and suddenly things like speed bumps were out of favor. In any case, Monderman did not have the budget for traffic-calming infrastructure. At a loss, he suggested that the road simply be made more “villagelike.” Maybe if the road looked more like a village road and less like the highway leading out of town, people would act accordingly. The village, coincidentally, had called in some consultants to redesign the village itself. Why not extend the treatment to the road? Working with the consultants, Monderman offered a design. “I thought, this must go wrong. There were no flowerpots, no chicanes. It was just a simple road in a village, nothing more.” A month after the project was finished, Monderman took a radar gun and measured the speed of cars passing through the village. In the past, with his chicanes and flowerpots, he would have been lucky to get a 10 percent drop in speed. This time, the speed had dropped so much that he could not get a reading. “The gun only functioned at thirty kilometers per hour,” he recalled.

What had happened? Monderman, in essence, had created confusion by blending the car, bike, and pedestrian realms. What had been a wide road with clearly marked delineations was suddenly something more complex. “The width of the road is six meters,” Monderman told me as we stood on the sidewalk in Oudehaske. “That makes it impossible for two cars to pass each other together with a bicycle. So you’re forced to interact with other people, negotiate your behavior.” What adds to the complexity is that the road, now made of small paving blocks to give it a “village feel,” is two-tone: The center segment is red, and two small “gutter” strips running alongside are gray. Even though the strips are slightly curved to channel water, they are perfectly usable. “So when you look at the street it looks like a residential street of five meters,” Monderman explained. “But it has all the possibilities of a six-meter street. You can use it for all the traffic.” There is also, noticeably, a quite low curb. “The height of the curb is very low because both of the parts are parts of the one scheme,” he said. “We have the feeling we belong to one another. When you isolate people from each other by a high curb, ‘This is my space, this is mine,’ drivers drive faster. When you have the feeling that at this moment a child could drop in front of my car, you slow down.”

Monderman’s experiments were seminal steps in what would become known as “psychological traffic calming.” Rather than hit people over the head with speed bumps they would resent and signs they would ignore, better results could be achieved if drivers were not actually aware that they were slowing down, or why. “Mental speed bumps” is the delightful phrase used by David Engwicht, a gregarious traveling Australian traffic activist who for years had been tinkering, on a less official basis, with ideas similar to Monderman’s—even though neither knew each other at the time.

Instead of speed bumps, which tell drivers to drive as fast as they can before they hit the next speed bump, Engwicht argues that intrigue and uncertainty—the things that active cities are filled with—are the best remedies for traffic problems. Put a child’s bike on the side of the road instead of a speed bump; hang a weird sculpture instead of a speed-limit sign. One of Engwicht’s signature tactics is to set up a “Street Reclaiming Chair,” a bright throne of sorts, in the middle of a local street and then, wearing a large colorful crown, chat with passing drivers who, not surprisingly, have slowed. The Danish Road Safety Council got at this idea in a different way in a film a few years ago that showed a mock new traffic-calming scheme: topless Danish models standing on the side of the road holding speed-limit signs. In this case, the “flashing” signs worked quite well.

More than twenty-five years after the Oudehaske incident, the speed through the village is the same—and no one has had to take off their shirts. “That experience changed my whole idea about how to change behavior,” Monderman told me. “It proved that when you use the context of the village as a source of information, people are absolutely willing to change their behavior.” Monderman was, in essence, thinking like an architect in a realm that had been handed over entirely to engineers. In constructing a building, engineers are essential to making it function, but it is architects we call upon to determine how the building will be used, to organize the space. “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?

Monderman continued to toil away in relative obscurity, his non-traditional techniques tolerated in small doses. 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.

As one looks longer, it becomes clear how well it all flows. No one ever seems to come to a stop, neither cars nor cyclists. “Sometimes a car has to slow down, you think he’s stopping—no, he’s creeping and is going on again. You actually see all the brains of people working together in a much more organic, fluid way,” said Monderman. Then he demonstrated one of his favorite tricks. He began to walk into the roundabout, continuing our conversation. He walked backward. He closed his eyes. It may have just been unnatural Dutch patience at work, but cars, already on the lookout for other cars and cyclists, seemed to regard him as just another obstacle to interact with, and so they steered around him, slowly. “What is nice,” he noted, “is that even in the strongest traffic-oriented type of crossing, behavior can be steered by the context.”

This seemed a kind of group enactment of the traffic experiments Ian Walker had conducted on the roads in Bath. People were taking stock of one another, making decisions, and acting accordingly in the moment. Ben Hamilton-Baillie, an English transportation planner who has allied with Monderman in a movement known as Shared Space, talks about seeing scores of little moments in Drachten like the one in which a Dutch mother on a bike, carrying a kid, merges in front of a big truck with little more than the smallest flicker of eye contact and the slightest lift of a finger. To many people, this might seem scary, perhaps even slightly insane. And maybe just Dutch.

Hamilton-Baillie suggests that there is something crucial in the fact that above 20 miles per hour, humans begin to lose eye contact. “As social creatures it is incredibly important for humans to exchange rapid messages about status and other traits,” he says. “I’ve spent a lot of time watching the junction. What are the rules? There’s clearly a hierarchy. If you were a confident young businesswoman in a suit you sailed straight through; if you were a hesitant tourist you waited. Your position in the hierarchy could apparently be established in a microsecond.” But all this has to happen at human speeds. The faster we drive, the less we see. Hamilton-Baillie suggests that it is more than coincidental that as drivers get above 20 miles per hour, we lose eye contact with pedestrians, while our chances of dying as pedestrians if hit by a car also begin to soar dramatically. As humans with an evolutionary history, we are presumably not meant to move faster than we can run, which tops out at around 20 miles per hour. In the modern world, Hamilton-Baillie adds, this may explain why being struck by a car becomes so much more exponentially deadly above that speed.

Monderman insisted that what he was doing was not anarchy. Instead, he said, he was replacing the traffic world with the social world. “I always say to people: I don’t care if you wear a raincoat or a Volkswagen Golf, you’re a human being, and I address you as a human being. I want you to behave as a human being. I don’t care what kind of vehicle you drive.” People, his argument goes, know what a roundabout looks like, and they know what its rules are, so why should they be told again? If they’re unsure about what to do or feel insecure, they can do what people do in any situation where they’re unsure or insecure, be it a cocktail party or the first day of school: Learn by watching others, and proceed cautiously.

This gets to the heart of a controversy about how to make traffic safer. Not everyone acts cautiously. People do drive like idiots. As I argued in the first chapter, traffic makes it hard for us to be human. Drivers, insulated in their anonymous cocoons and holding a three-thousand-pound advantage, kill hundreds of pedestrians every day around the world. Would it not be better to segregate people and cars and bikes to the greatest extent possible? Would it not be better to have as many signs, lights, guardrails, signals, bollards, and zebra crossings as possible?

Hamilton-Baillie does not agree that drivers are incapable of understanding social norms and conventions and need to be under the constant control of mechanical devices and signs. “You can quite quickly instill in children a sense of what’s appropriate when you can fart and when you can’t,” he explained one night in a restaurant in the Dutch city of Groningen. “What you get by transferring the control systems to cultural or social norms [is that] you then empower other people to tackle the issue themselves. If someone was misbehaving in here, there would come a point at which someone would say, ‘C’mon, mate, get out of here.’” But anyone driving the roads today can see that many people do not obey social conventions, or even laws. “Of course there will be people who ignore those conventions,” he said. “Such behavior will exist even in a legislated context. But you don’t control teenage joyriding through legislation.”

Most of our daily life is governed by social conventions. In the elegant Tiffany store on Fifth Avenue in New York, there aren’t any “No Spitting” signs, but there are probably few people who choose to expectorate there (and not simply because a security guard would toss them out). To return to the queues of the last chapter, when one enters a McDonald’s there are no signs that say, “Do Not Cut in Line.” But chances are people do not (of course, in some places they may, but this is a point I’m saving for Chapter 8). I can hear you protesting: People violate social conventions every day. They talk on their cell phones when signs ask them not to. And traffic is dangerous. How could you take the “Yield” sign away from a roundabout and not cause chaos? How would people figure out how to negotiate the crossing without traffic signals? If anything, we need more signals and signs!

We have a strange, almost fetishistic belief in the power of signals. If a visitor from a planet without cars were to visit Earth, he might be truly perplexed by the strange daubs of paint on the street, the arrows blinking in the air. Do you remember the children’s game Red Light, Green Light? The person acting as the stoplight would stand with his back to the other players and announce, “Green light.” The players would move forward. Then he would say, “Red light” and spin around. If you didn’t stop before he saw you, you were “out.” What makes the game work is that children do not always stop in time. Nor do adults in real life, which is even more complicated, because we have things like yellow lights—do I stop or do I go? A line on the street or a light in the air may keep cities from getting sued (as long as it doesn’t malfunction), but it does nothing to prevent a driver from misbehaving, perhaps even killing someone. Traffic signals assign priority; they do not provide safety. The high number of people killed by drivers running a red light—the sort of thing a roundabout with a nice big fountain in the middle tends to cure—is proof enough of this.

Or consider, for a moment, the urban pedestrian “Walk” signal. Surely this seemingly enlightened bit of design must be vital to the safety of people on foot? Yes, except that at most intersections it happens to accompany the invitation for drivers to make a turn. The result is that every year, many pedestrians, correctly believing themselves to have the right-of-way, are killed while walking in the crosswalk by perfectly sober drivers who have paid slavish attention only to their own green light. (Or they may have had their view obscured by their car’s roof pillar, a problem particularly in left turns, when the pillar looms in the center of the driver’s vision.) Things are even worse where right turns are permitted on red; for drivers, rights on red may be the only “cultural advantage” of Los Angeles, as Woody Allen joked, but studies have shown that they are a distinct disadvantage for the health of pedestrians. The sad fact is that more urban pedestrians are killed while legally crossing in crosswalks than while jaywalking. Granted, the number of people who use the crosswalk is higher, but this does not diminish the point that more pedestrians are killed in New York City while obeying the law than while not.

Careful jaywalking, particularly on one-way streets, can be safer than confident crossing at the crosswalk (where the pedestrian may have to worry about streams of traffic from different directions). A similar phenomenon seems to occur at the crosswalks one finds at places without traffic signals. Confusingly, there are two types; they seem different but are legally the same: “marked” versus “unmarked.” Marked crosswalks are easy to identify: two lines across the pavement. In most jurisdictions in the United States and elsewhere, unmarked crosswalks exist at any place, like intersections, where there are connecting sidewalks on either side of the street. Even though there may be no visible crosswalk line connecting the sidewalks, legally, there is: Drivers must yield to crossing pedestrians, even at intersections that are “uncontrolled” (i.e., there are no stop signs). One might think that marked crosswalks, which send clear signals to all, would be preferable. But marked crosswalks are actually no safer than unmarked crosswalks, and in some cases are actually more dangerous, particularly when pedestrians, like the hero of the old video game Frogger, must navigate several lanes.

Studies do show that motorists are more likely to yield to pedestrians in marked crosswalks than at unmarked crosswalks. But as University of California, Berkeley, researchers David Ragland and Meghan Fehlig Mitman found, that does not necessarily make things safer. When they compared the way pedestrians crossed at both kinds of crosswalks on roads with considerable traffic volumes, they found that people at unmarked crosswalks tended to look both ways more often, waited more often for gaps in traffic, and crossed the road more quickly. Researchers suspect that both drivers and pedestrians are more aware that drivers should yield to pedestrians in marked crosswalks (even though 35 percent of drivers polled did not know this). But neither are aware of this fact when it comes to unmarked crosswalks. Not knowing traffic safety laws, it turns out, is actually a good thing for pedestrians. Because they do not know whether cars are supposed to stop—or if they will—they act more cautiously. Marked crosswalks, by contrast, may give pedestrians an unrealistic picture of their own safety.

If signs and symbols do not always achieve their intended results, removing road markings can have surprising effects. White lines on the road are commonly thought to be a fundamental element of a safe road. Indeed, on high-speed roads they are essential. Drivers are able to travel at high speeds without crashing into one another or running off the road only if they have a consistent sense of their lane position. Think of the nervous moment, as you’re approaching a toll station, when all the lines disappear and the road opens into a vast alluvial fan (not to mention the equally disturbing confusion on exiting as everyone jockeys for position).

But what about on roads with 30-mile-per-hour speed limits? Don’t we still need lines to keep people in their own lanes and to prevent them from smashing into one another? A study in England’s Wiltshire County looked at two similar roads, one that had a center line, and a narrower one on which the line had been removed. Drivers actually did a better job of staying in their own lane on the road with no center line. Even though the road with no center line was narrower than the road with a line, vehicles still managed to stay farther away from oncoming vehicles (by 40 percent) than on the road with a line. They also tended to slow down in the face of oncoming traffic. 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. (This suggests that no bicycle lanes are better for cyclists than insufficiently wide bicycle lanes.)

Hans Monderman was quite aware that by removing signals and markings, he made people feel more at risk in the Laweiplein. This was a good thing. “We feel it is unsafe,” residents told him. “I think that’s wonderful,” he told me. “Otherwise I would have changed it immediately.” There would even be a benefit to some crashes, he added: “I hope that some small accidents happen, as part of the learning process of society.” Monderman was delighted when his son had his first minor mishap in a car. In fact, he said, he would have paid for him to have it: “He knows that he is vulnerable, with his own responsibility for his behavior. Having an accident should be part of the driving course. I think that these small accidents help in avoiding severe accidents.”

But here is the funny thing. Since the Laweiplein was converted into a “squareabout,” the number of crashes, according to a preliminary study by the local technical college, has dropped. In 2005, there were none at all. Well, that’s because everyone is moving more slowly, right? Perhaps. But there are a few other interesting facts. Since the conversion, the average time to cross the intersection has dropped by 40 percent, even as traffic has increased. The time buses had to wait to get through has been cut by as much as half. All traffic, the college found, seems to move at a constant flow, and even at peak hours, the movement is steady, if slow—and any traffic engineer will tell you how important it is for drivers to be able to sense progress. The report noted something else interesting: More cyclists were using hand signals when moving in the roundabout; this, the report claimed, was unusual behavior in the Netherlands. More drivers were using their signals, as well. The responsibility for getting through the intersection was now up to the users, and they responded by communicating among themselves. The result was that the system was safer, even though the majority of users, polled in local surveys, felt that the system was more dangerous!

In changing the design in Drachten, Monderman was really asking, What is this street for? What are cities for? Monderman had said he would never widen the streets leading into the Drachten crossing. People were coming for the city, not for the traffic. “Cities are never roads” is how Joost Váhl describes it. Freed from a sense that they are in a city or a village, and instead are simply on a road, drivers respond in kind. They take their information not from local context but from standardized signs. “When you removed all the things that made people know where they were, what they were a part of, then you had to explain things,” Monderman said.

There can be a power in not explaining things. In Culemborg, Váhl and I, joined by Hamilton-Baillie, pedaled out to a crossing on the outskirts of town where a long, straight highway comes into the village. Marking the crossing are two yellow lights that rise out of the ground. They are actually lanterns, of the sort hung around the canals in the Dutch city of Utrecht, turned upside down. They’re not standard traffic devices. Váhl installed them in an effort to get drivers to slow down as they careened in off the rural highway. “It’s making clear that there is something strange,” he told me. “It’s not common that there are lights like this.” But doesn’t the strange become familiar quickly? That’s why Váhl placed them so close together. It looks as if two cars may not make it through. But, as Váhl explained, with a hint of whimsy, “It is four meters and twenty in between the yellow things. It makes it possible that you don’t hit the mirror of the other car.” With practice the drivers may get used to this as well—but how can they be sure that the approaching driver is a local? Best to slow down.

What if, instead of the strange lanterns, approaching drivers were faced with a speed-limit sign? First, they might not even look at it. Second, they might worry about getting a ticket, but perhaps experience has taught them there is usually no cop there. Third, a speed-limit sign just announces a number. It says nothing about the fact that one is now in a village, where children or bicyclists might be present. Nor does it communicate risk. Forcing drivers to slow down, in order to save their own skins, just might be the best way to help save others’ skins.

All this crazy stuff might be fine for provincial Dutch cities and English villages, with their relatively low traffic volumes and speeds. And in the Netherlands, where 27 percent of daily local trips are made on bicycles, drivers are much more experienced in interacting with cyclists. This sort of thing simply would not work in a large city in another country, you might think. Or would it?

Kensington High Street, the main commercial thoroughfare in one of London’s poshest neighborhoods, is worth taking a look at, as I did one day with Peter Weeden, a senior engineer with the Traffic Section of the Royal Borough of Kensington and Chelsea. By the 1990s, Weeden recalled, the street was in a sorry state, and merchants were concerned about losing business to a large new shopping development being planned nearby. There was little aesthetic coordination, with the streets and sidewalks a jumble of different materials. “There was lots of clutter and street signs,” Weeden explained. “They were put up with the best of intentions, but always on a very piecemeal basis. Someone comes along and puts up a sign for speed humps, someone else comes along and puts up another. Over time you end up with a forest of signs, most of which, it turns out, are not actually required.”

The borough wanted the street to look better, but not at the expense of traffic flow or safety. “As well as being a shopping and residential high street, it’s also one of the main arterial routes in and out of West London,” said Weeden. Some 2,500 cars course down the street in a busy hour, while as many as 3,000 pedestrians spill out of the main tube station. Where the usual approach would have been to dig into the trusty traffic engineer’s “toolkit,” this time the Kensington planners began by throwing out everything that had been done before. “What we did was to actually strip out ninety-five percent of the signs in Kensington High Street,” said Weeden.

They wanted to see what was really necessary and what was simply there because some engineer assumed it had to be. The guardrails lining both sides of the street, a not uncommon sight in London, were also removed in an effort to reduce visual clutter. “There is a very strong case for taking out guard railing,” noted Weeden. “Wheelchair users don’t like it; there are vision problems. Cyclists don’t like it; they can get trapped between the vehicle and the rail if they get cut off. And the segregation between travel modes has been found to increase vehicles’ speeds—you think you’re going to own that space.” The plan was not without critics—including the city’s department of traffic engineering. “Transport for London thought we were taking unacceptable risks,” Weeden said. But the Kensington engineers were not just casually saying, “Let’s rip out all the traffic signs.” They began by altering only a small test section, then waited to see what would happen.

Walking down the street, I noticed, as with Drachten, how much more clean and pleasant it looked without all the traffic markings, railings, and signs. It felt more like a city street should, and not like a slalom course for cars or a veal pen for pedestrians. The sidewalk felt connected to the street. There were several traffic lights, and while some pedestrians did cross at the light, there was no marked zebra crossing. Most people crossed elsewhere, in any case. No longer steered toward the crosswalk by the railing, they crossed where they chose to, navigating their way through the slow but steady flow of cars, buses, and bikes, pausing halfway on a center island.

Having tossed away the bulk of the safety improvements put in over the years for cars and for pedestrians, what happened? Chaos and destruction? Quite the reverse. Pedestrian KSIs (“killed or seriously injured”) dropped 60 percent, with a similar decline for minor injuries. Weeden and his colleagues were as surprised as anyone. “The scheme itself never set out to be an accident-reduction scheme,” he told me. “It was really just for aesthetic reasons, to encourage people to shop there. As a by-product we found that accident rates had dropped.”

By making the street look better, they also made it safer. Perhaps this is not an accident. Cities are meant to be places for mixing with others, for improvised encounters, for observing details at a human scale. (Hamilton-Baillie says that London taxi drivers he interviewed reported liking the new scheme without quite knowing why, though they did cite the presence of “pretty girls” as a positive.) “This world of standardized, regulated kit—traffic islands, bollards, road markings, safety barriers, signs, signals—it’s all a world completely separated to whatever happens behind it,” said Hamilton-Baillie. “It’s a world that we have been taught, and created policy, to say is an alien world. You’ve got to press a button to get permission to cross it.” Drivers, absolved from their social responsibility by the mandates of the traffic world, accordingly act in antisocial ways. Pedestrians, tired of being steered far out of their way to cross the street or being inordinately delayed by cars in the many cases where they are the majority, rebel against the safety measures that have supposedly been erected for their benefit. The safety measures cause drivers and pedestrians to act in more dangerous ways.

A favorite example for Hamilton-Baillie of how things can be different is Seven Dials in London, the small circular junction in the Covent Garden district where seven streets converge. At a small plaza in the center, marked by a sundial, it’s not uncommon to find people eating their lunch or to see them strolling across the roundabout, even as cars navigate their way slowly around the space. There are no guardrails protecting the pedestrians sitting in the center from the road. There are no speed bumps on the approaches. There are no signs warning, PEOPLE EATING LUNCH AHEAD. Rather, the uncertainty of the space and its human-scaled geometry dictate the behavior. There is an element of mystery and surprise, one that Charles Dickens remarked upon over a century before in Sketches by Boz: “The stranger who finds himself in the Dials for the first time…at the entrance of Seven obscure passages, uncertain which to take, will see enough around him to keep his curiosity awake for no inconsiderable time.”

That awakened curiosity is still present today, and for drivers and pedestrians it translates into a need to pay attention. Even as a pedestrian navigating the Dials, I found myself confused. Which of the seven streets led to the Tube? If only there was a sign to point the way. Instead I paused, looked around, and decided to take the road that had the most people on it. This was the social world, and I was relying on human instincts. My choice was correct, and I found the Tube.

Forgiving Roads or Permissive Roads? The Fatal Flaws of Traffic Engineering

One of Hans Monderman’s many interesting ideas about traffic was that it is a network not only in space but in time. What this means is that the farther we drive, the faster we expect to be able to go. “When I start at home, I drive very slowly,” he told me. “All my neighbors know me, they are part of my world, and I part of theirs, and it’s absolutely unacceptable that I speed in my own street. But after a few minutes, I’m a bit more anonymous, and the more anonymous I get, the more my foot goes down and I’m speeding more and more.” At the beginning of his trip, he was in the social world, and at the end of it, perhaps arriving in another village, he was as well. But what about the in-between? This was when he appreciated the traffic world, with all its signs and markings and safety measures and speeds. “When you want nice villages,” he noted, “you need freeways.”

But there is a problem with that in-between. Sometimes the roads on which people drive fast, as if they are the restricted-access highways of the traffic world, still have elements of the social world. People live near them, do their shopping on them, perhaps even have to cross them on foot. “I always say the road in-between is the most dangerous road,” Monderman remarked. “It’s not a highway, but it’s not a residential street. All these roads have the biggest accident problem. The road is often telling you this is a traffic system: We have organized everything around you for all your needs. But the same road is cutting as a knife through the social world. The traffic world and the social world are shouting at each other.”

One finds a striking example of this situation not in the Netherlands but in Orlando, Florida. Dan Burden is a widely acclaimed traffic guru who now works with the Orlando transportation planning firm Glatting Jackson. We were cruising down East Colonial Drive, which is the Orlando stretch of U.S. Highway 50, heading for Baldwin Park, a New Urbanist community built on a former naval base that Burden was eager to show me. Burden, famously known for his elaborate walruslike mustache, was newly clean-shaven (“It’s for charity,” he explained). As we drove, Burden gave a running commentary on the nature of the street, which bears a dubious distinction: One analysis found it to be the twelfth-deadliest road in America. (The deadliest road, according to another survey, is U.S. 19, also in Florida, a few hours away.)

In the beginning, we were in the urban section of East Colonial Drive, which runs through the heart of north Orlando. It looked a bit like Los Angeles, a mixture of strip malls with a smattering of people on the sidewalks. Buildings were not set back very far, and the road was lined with concrete utility poles and other obstacles. As we passed a speed-limit sign, I did a double take. It read, 40 MPH. That struck me as strange. We were driving in what seemed to be a place that would be posted for 35 at the most. This is not uncommon in Florida, according to Burden. “If you looked on a city-by-city basis, county by county, you’re going to find our high speeds are seven to fifteen higher than they will be in most states.”

Continuing on Colonial, we entered the historically newer sections of town, and the road began to change subtly. The lanes became wider, the speed limit was raised to 45, and the sidewalks, when they existed at all, were dozens of feet from the road. “Notice how far back the sidewalk is,” Burden exclaimed. “What is it, fifty feet? It’s so far back it’s like another world. There’s no trees, and they’ve pushed the clear zone as far back as they could.” Pulling into the parking lot of a Circle K convenience store, we saw a small white memorial posted in the swath of grass between the road and the gas pumps. Florida, somewhat controversially, is one of the few states that allows family members to place memorials on the site of fatal crashes. (The states that don’t cite reasons ranging from the perceived safety risks of the memorials themselves to highway aesthetics.) It wasn’t the first memorial I had seen. But I hadn’t seen any in the more downtown part of Colonial Drive. Had I just not looked carefully enough, or was something else going on?

Colonial Drive is a tale of two roads. The first section of the road, with its narrow lanes, many crosswalks, thicker congestion, and bountiful collection of utility poles, parked cars, and other hazards, is the kind of road conventional traffic engineering has judged to be more dangerous. More people packed more tightly together, more chances for things to go wrong. The newer section of Colonial, with its wider lanes, its generous clear zones (i.e., roadsides without obstacles), its less-congested feel, and its fewer pedestrians, would be judged to be safer.

But when Eric Dumbaugh, an assistant professor of urban planning at Texas A&M University, did an in-depth analysis of five years’ worth of crash statistics on East Colonial Drive, his results were surprising. He looked at two sections: what he terms a “livable” section, with the narrower lanes and lack of clear zones, and a section with wider lanes and more generous clear zones. In many respects, the two sections were similar, and thus ideal for comparison: They had the same average daily traffic, the same number of lanes, and the speed limits were similar (40 miles per hour versus 45). They had similarly sized painted medians in between the opposing streams of traffic, and the lengths of roadway were the same. They’d even had the same number of crashes at intersections, and the age of the at-fault drivers in those crashes was the same.

When Dumbaugh looked at the number of midblock crashes, precisely those types that should be reduced by the safety features of the road with wider lanes and wider clear zones, he found that the livable section was safer in every meaningful way. On the livable section, there had not been a fatality in five years (and hence there were no white memorial markers). On the comparison section, there had been six fatalities, three of them pedestrians. The livable section, which offered a driver many more chances to hit a “fixed object,” had fewer of these crash types than the section designed to avoid those crashes. What about cars crashing into other cars? Surely the livable section, with all its drivers slowing to look for parking or coming out of parking spots, with all those cars packed tightly together, must have had more crashes. But across the board, from rear-end crashes to head-on crashes to turn-related crashes to sideswipe crashes, the numbers were higher in the section that the conventional wisdom would have deemed safer.

Why might this be so? Without a detailed reconstruction of each crash, it is impossible to be certain. But there are plausible hypotheses. Speed is a prime suspect. The wider lanes and lack of any roadside obstacles in the comparison section make 45 miles per hour seem optional, and some drivers are hitting near-highway speeds as other drivers are slowing to enter Wal-Mart or coming out of Wendy’s. The painted median down the middle, known colloquially as a “suicide lane,” allows people to make turns wherever they like. But these turns are across several lanes of oncoming high-speed traffic, and as we saw in Chapter 3, choosing safe gaps is not often an easy task for humans.

For pedestrians, a seemingly trivial variance in a car’s speed can be the difference between life and death. A Florida study found that a pedestrian struck by a car moving 36 to 45 miles per hour was almost twice as likely to be killed than one struck by a car moving 31 to 35 miles per hour, and almost four times as likely as one struck by a car moving 26 to 30 miles per hour. In the livable section, pedestrians have an ample number of crosswalks, placed closely together. In the newer section, there are few crosswalks, and the ones that do exist are found at large intersections with multiple lanes of turning traffic. The “curb radii,” or the curves, are long and gentle, enticing drivers to take them quickly, and do nothing to remind drivers about the pedestrians that may be legally crossing with the signal around that bend. In the livable section, drivers must slow to take tight turns, and parked cars buffer pedestrians from cars that veer off the road—not to mention that parked cars themselves cut speeds by some 10 percent.

Dumbaugh’s research challenges a school of thought that has long held an almost unassailable authority in traffic engineering: “passive safety.” This line of thinking, which emerged in the United States in the 1960s, says that rather than trying to prevent crashes, highway engineers (as well as car makers) should try to reduce the consequences of crashes, or, as one highway manual put it, “to compensate for the driving errors [the driver] will eventually make.” Engineers running cars on “proving ground” test roadways found that once they departed the roadway, cars came to a stop an average of thirty feet off the road—so this became the standard minimum “clear zone,” that section of legally required nothingness beyond the edge marking and before any obstacle. At General Motors, a “crash-proof highway” was designed with one-hundred-foot clear zones. Its engineer was so impressed with the performance that he declared, “What we must do is operate the ninety percent or more of our surface streets just as we do our freeways…[converting] the surface highway and street network to freeway and proving ground road and roadside conditions.”

In many cases, like on East Colonial Drive, that is exactly what happened. The traffic world was brought to the social world. The design is well in line with the stated current engineering guidance: “The wider the clear zone, the safer it is.” But far from ensuring safety, the road was home to more crashes than the section of the street that looked more like a traditional city street, even though the traffic was similar. What went wrong?

Part of the problem may be the in-betweenness of the newer sections of East Colonial. Walter Kulash, another noted traffic engineer with Glatting Jackson, says traffic engineers are not always to blame. Roads like Highway 50, he told me, are being used in ways engineers never intended. Designed as arteries to ferry people from one city cluster to another, they have instead become the “Main Streets” for suburban sprawl, lined with busy shopping centers and strip malls. “The engineers had nothing to do with that development, fronted by parking, for miles along the arterials, like you saw on Colonial Drive,” Kulash said. “That is highly injurious to the function of the highway. The fact that fifty thousand travelers a day are bundled together, thereby making that irresistible to commerce, you might say, Okay, who’s responsible for that? But you can hardly say a majority of blame ought to go to highway engineers.”

From a strict engineering perspective, the “proving ground” approach makes sense. As Phil Jones, a traffic engineer based in the Midlands of England, argues, engineers are taught to work in “failure” mode. To design a bridge on a highway, engineers calculate the loads the bridge will need to carry, find out at which point the bridge would fail, and then make it more safe than that, for redundancy. But what happens when the factors involved are not just loads and stresses but the more infinitely complex range of humans behind the wheel?

In designing the approach path to a T-intersection, engineers use the factor of driver reaction time to determine what the appropriate sight distance should be—that is, the point at which the driver should have a clear view of the intersection. The sight distance is typically made longer than needed, to accommodate drivers with the slowest reaction times (e.g., the elderly). As with the highway bridge, the road design has a safety cushion to help it withstand extremes. So far, so good. But designing the road for slow reaction times, Jones explains, creates “very long sight distances, so someone who’s younger and more able and can react faster than that will consume that benefit. What the safety model doesn’t recognize is that yes, the elderly person will react more slowly, but they’re not the ones driving fast in the first place. You’re giving license to people to drive more quickly.” This may be why, as studies have shown, railroad crossings where the sight distance is restricted—that is, you can see less of the track and the oncoming train—do not have higher crash rates than those with better views. Drivers approached the tracks more quickly when they felt it was safer.

What is meant to be the “forgiving road,” argues Dumbaugh, becomes the “permissive road.” Safety features meant to reduce the consequences of driver error encourage drivers to drive in a way requiring those generous safety provisions. Sometimes, passive-safety engineering makes things more dangerous. Dumbaugh studied a Florida road on which a number of cars had crashed into trees and poles. Simple, right? Just get rid of the obstacles and make the clear zones bigger. Looking carefully at the crash records, however, Dumbaugh found that the majority of crashes happened at intersections and driveways, as cars were turning. Were the obstacles the problem or was it, as Dumbaugh suggested, that drivers were unable to complete the turn because they were traveling too fast as they entered the turn, at the high speed the road design was telling them was “safe”?

In both Drachten and London, choices were made to remove traffic-safety infrastructure like signs and barriers. These choices were influenced by aesthetics, but they had the perverse outcome of making things safer. The problem with applying typical highway-engineering solutions to cities, villages, and the other places people live is that the same things that often signify “livability” are, in the eyes of a traffic engineer, “hazards.”

Take the case of trees. In my Brooklyn neighborhood, they add to the desirability of a street. They raise property values. They may protect pedestrians from wayward cars. Yet they’re also a common bane of traffic engineers, who have been—perhaps with the best of intentions—removing them from roadsides for decades. While many people have indeed died from colliding with trees, there is nothing inherently dangerous about a tree. What matters is the context. In his research Dumbaugh looked at a section of a road in Florida that travels through Stetson University. It’s lined with mature trees, a few feet from the road. In four years, Dumbaugh found, there was not a single crash. What’s more, he observed, most cars traveled at or even below the speed limit of 30 miles per hour (which many studies—and probably your own experience—have shown is rarely the case in cities). The hazards were the safety device. Drivers left with little room for error seemed quite capable of not making errors, or at least driving at a speed that would help “forgive” their own error.

The tree-lined road goes against the typical engineering paradigm, which would have deemed the trees unsafe and in need of removal. With the trees (the potential source of system failure) removed, a typical pattern would have happened: Speeds would have increased. The risk to pedestrians (students at Stetson, mostly) would have gone up; perhaps a pedestrian would have been struck. The police would have been called in to set up speed traps. Eventually, vertical deflection—a.k.a. speed bumps—would have been installed to calm the traffic. Having made the road safer, new measures would have been needed to again make it safe.

The pursuit of a kind of absolute safety, above all other considerations of what makes places good environments, has not only made those streets and cities less attractive, it has, in many cases, made them less safe. The things that work best in the traffic world of the highway—consistency, uniformity, wide lanes, knowing what to expect ahead of time, the reduction of conflicts, the restriction of access, and the removal of obstacles—have little or no place in the social world.