Traffic_ Why We Drive The Way We Do Part 6

This kind of information, along with the data gathered from various loops and sensors, can be used to make precise forecasts about what traffic will be like not only on "normal" days but when crashes or incidents occur. There is, however, a problem: Does the forecast itself change the way people will behave, thus changing the forecast? As the economist Tim Harford notes about Wall Street forecasting, if everyone knew today that a stock was going to rise tomorrow, everyone would buy the stock today-thus making it so expensive it could no longer rise tomorrow.

Shreckenberg calls this the "self-destroying prognosis." In his office at the University of Duisburg-Essen, he points to a highway map with its roads variously lit up in free-flowing green or clogged red. "The prognosis says that this road becomes worse in one hour," he says. "Many people look at that and say, 'Oh, don't use the A3.' Then they go somewhere else. The jam will not occur since everyone turned to another way. This is a problem." These sorts of oscillations could happen with even short lags in information, in what Shreckenberg calls the "ping-pong effect." Imagine there are two routes. Drivers are told that one is five minutes faster. Everyone s.h.i.+fts to that route. By the time the information is updated, the route that everyone got on is now five minutes slower. slower. The other road now becomes faster, but it quickly succ.u.mbs to the same problem. The other road now becomes faster, but it quickly succ.u.mbs to the same problem.

This raises a question: Has the information provided actually helped drivers or the system as a whole-or has it triggered the "selfish routing" mentioned before? Moshe Ben-Akiva, the director of MIT's Intelligent Transportation Systems program, has studied such travel behavior issues for decades. He calls traffic predictions a "chicken-and-egg problem." "The correct prediction must take into account how people are going to respond to the prediction," he says. "You cannot predict what will happen tomorrow without taking into account how people are going to respond to the prediction once the prediction is broadcast."

And so researchers create models that antic.i.p.ate how people will behave, based on how they have behaved in the past. Shreckenberg, in Germany, wonders if this means, in essence, not giving drivers the whole picture. "You have to structure the information. What you want is for the people to do certain things. Telling them the whole truth is not the best way." This is something on the minds of the big commercial providers of traffic information. As Howard Hayes, vice president of NAVTEQ, said at the firm's headquarters in Chicago, "What happens if once this really good predictive traffic information becomes available, everyone starts getting shunted over to a different direction, which itself becomes jammed? Ideally you need something sophisticated, so that a certain number of people get shunted to one route and others to another."

Since the information is still so limited, and since so few people actually have access to it, we do not really know how it will all play out once everyone is able to know the traffic conditions on every road in a network. Most simulations have shown that more drivers having more real-time information-the closer to actual real-time, the better-can reduce travel times and congestion. Even drivers without without real-time information can benefit, it is argued, because better-informed drivers will exit crowded roads, thus making those roads less crowded for uninformed drivers stuck in traffic. But as you might expect, studies suggest that the benefit for any one driver with access to real-time information drops as more people have it. This is, in essence, the death of the shortcut. The more people know the best routes at all times, the less chance of there being some gloriously underutilized road. This is good for all drivers (i.e., the "system") but less good, say, for the savvy taxi driver. real-time information can benefit, it is argued, because better-informed drivers will exit crowded roads, thus making those roads less crowded for uninformed drivers stuck in traffic. But as you might expect, studies suggest that the benefit for any one driver with access to real-time information drops as more people have it. This is, in essence, the death of the shortcut. The more people know the best routes at all times, the less chance of there being some gloriously underutilized road. This is good for all drivers (i.e., the "system") but less good, say, for the savvy taxi driver.

Real-time traffic and routing is most valuable, it has been suggested, during nonrecurring congestion. When a road that is normally not crowded is backed up because of a crash, it's useful to know of better options. During recurring congestion, however, those peak-hour jams that result from too many people going to the same place at once, the advantage shrivels once the tipping point of congestion has been pa.s.sed. (It is most effective right on the brink, when alternative routes are on the verge of drying up.) In a traffic system that is always congested, any good alternative routes will have already been discovered by other drivers.

Another shortcoming of real-time routing is due to a curious fact about urban road networks. As a group of researchers observed after studying traffic patterns and road networks in the twenty largest cities in Germany, roads follow what's called a "power law"-in other words, a small minority of roads carry a huge majority of the traffic. In Dresden, for example, while 50 percent of the total road length carried hardly any traffic at all (0.2 percent), 80 percent of the total traffic ran on less than 10 percent of the roads. The reason is rather obvious: Most drivers tend to drive on the largest roads, because they are the fastest. Even though they may have slowed due to congestion, they are still fastest. Traffic engineers, having built the roads, are generally aware of this fact, and would rather have you stay on the road that was designed for heavy use, instead of engaging in widespread "rat runs" that play havoc with local roads.

Both the promise and the limits of real-time traffic and routing information were demonstrated to me one day as I drove on Interstate 95 in Connecticut, using real-time traffic information provided by TeleNav via a Motorola mobile phone. The phone had been cheerily giving directions, even offering an evolving estimated time of arrival. Suddenly, an alert sounded: Congestion ahead. I queried the system for the best alternate route. It quickly drew one up, then delivered the bad news: It would take longer longer than the route I was on. The road I was on, congested or not, was still the best. than the route I was on. The road I was on, congested or not, was still the best.

Real-time traffic and routing information and congestion pricing are two sides of the same coin. One tells drivers how to avoid traffic congestion; the other impels impels drivers to avoid traffic congestion. When the roads are congested, real-time information does little good, except to tell drivers, like the people in line for Disney World's s.p.a.ce Mountain, how long they can expect to wait. This alone may be enough of a social good. But real-time congestion information, provided by the very cars generating that congestion, promises something else. It can be used to calculate the exact demand for any stretch of road at any time. With congestion pricing, the traffic on the roads will finally be made to act like the traffic in things, with market prices reflecting and shaping the supply and demand. drivers to avoid traffic congestion. When the roads are congested, real-time information does little good, except to tell drivers, like the people in line for Disney World's s.p.a.ce Mountain, how long they can expect to wait. This alone may be enough of a social good. But real-time congestion information, provided by the very cars generating that congestion, promises something else. It can be used to calculate the exact demand for any stretch of road at any time. With congestion pricing, the traffic on the roads will finally be made to act like the traffic in things, with market prices reflecting and shaping the supply and demand.

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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, pa.s.sersby 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 partic.i.p.ate 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 hoger, hoger, 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 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 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, t.i.tled "Hll dej till Hoger, Svensson!" or "Let's All Drive on the Right, Svensson!" (after a stereotypically common Swedish surname). 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, t.i.tled "Hll dej till Hoger, 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 antic.i.p.ated, 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 G.o.d-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 felt less safe to Swedish drivers, and they seemed to react with more caution. 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 sh.o.r.es. 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, 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. 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 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. 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 Was.h.i.+ngton, 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 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 s.h.i.+ning; 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 a.s.sessment 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 pus.h.i.+ng 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 just that extra margin of safety left. 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 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 s.h.i.+nar, 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." 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 s.h.i.+nar, 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 curveb.a.l.l.s than when he is thrown a curveball after a steady diet of fastb.a.l.l.s. 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 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." 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, s.p.a.ce-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. 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. 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 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." 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, 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, 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. 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 a.s.suage complaints by neighborhood residents that people are speeding down their streets. They may have even been put up after a child was. .h.i.t 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 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 carca.s.s next to the animated sign-only then did drivers finally slow. 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 carca.s.s 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 flas.h.i.+ng signs equipped with sensors to detect the presence of deer, but these so-called dynamic signs are not only costly but p.r.o.ne 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, flas.h.i.+ng 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 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 munic.i.p.alities 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 Inst.i.tute, as if discussing the openness toward s.e.x 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 WELKOM. Finally, it says: VERKEERSBORDVRIJ 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 s.p.a.ce: 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 h.o.m.ogeneity. 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 s.p.a.ce." 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 pa.s.sing 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 munic.i.p.ality, 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 a.r.s.enal 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 b.u.mp, the steep, jarring obstruction that dates to the dawn of the car itself. With the exception of places like Mexico City, speed b.u.mps 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 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. 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 b.u.mps 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 Vahl, 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, Vahl recalled a series of outlandish stunts that ranged from a "dial-a-b.u.mp" service (citizens could call and request "b.u.mps" in front of their homes), to the staging of a bicycle accident ("we wanted to know if car drivers would stop and help or pa.s.s 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 s.p.a.ce"). These tactics, which were really investigations into how to get cars and people to coexist in cities, eventually made their way into genuine social inst.i.tutions. The most famous of these were the woonerven 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 d.i.c.kens 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 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, 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 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 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 woonerven woonerven got 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 got 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, woonerven, the sign implies, but drive less carefully everywhere else. 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 s.h.i.+fted, and suddenly things like speed b.u.mps 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 pa.s.sing 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 pa.s.s 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 s.p.a.ce, 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 b.u.mps 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 b.u.mps" 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 b.u.mps, which tell drivers to drive as fast as they can before they hit the next speed b.u.mp, 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 b.u.mp; 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 pa.s.sing 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 "flas.h.i.+ng" 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 s.h.i.+rts. "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 s.p.a.ce. "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 s.p.a.ce," Monderman said. "It's a circular pattern, and most cities have a grid. It doesn't fit in the s.p.a.ce; 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 s.p.a.ce 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 s.p.a.ce 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 s.p.a.ce, 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. 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. 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. 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 c.o.c.ktail party or the firs