Traffic_ Why We Drive The Way We Do Part 3

In the gorilla experiment, an added condition made subjects less likely to see the gorilla: when their job got harder. Some subjects were asked to count not just pa.s.ses but the types of pa.s.ses-whether they were "bounce pa.s.ses" or pa.s.ses made in the air. "You've made the attention task that much harder, and used up more of your available resources," Simons said. "You're less likely to notice something unexpected."

In driving, you might protest, we do not do such things as tally basketball pa.s.ses. Still, there may have been times when you were concentrating so much on looking for a parking spot that you did not notice a stop sign; or you might have almost hit a cyclist because she was riding against traffic, violating your sense of what you expected to see. And there is another activity, one that we increasingly often indulge in while driving, that closely resembles that very specific act of counting basketball pa.s.ses: talking on a cell phone.

Let me ask you two questions: What route did you take to get home today? And what was the color of your first car? What just happened? Chances are, your eyes drifted away from the page. Humans, perhaps to free up mental resources, tend to look away when asked to remember something. (Indeed, moving the eyes is thought to aid memory.) The more difficult the act of remembering, the longer the gaze away. Even if your eyes had remained on the page, you would have been momentarily sent away in a reverie of thought. Now picture driving down a street, talking to someone on a mobile phone, and they ask you to retrieve some relatively complicated bit of information: to give them directions or tell them where you left the spare keys. Your eyes may remain on the road, but would your mind?

Studies show that so-called visual-spatial tasks, such as rotating a letter or a shape in one's mind, cause our eyes to fixate longer in one place than when we are asked to perform verbal tasks. The longer the fixation, the thinking goes, the more attention we are devoting to the task-and the less we're giving to other things, like driving. The mere act of "switching" tasks-like moving from solely driving to talking on the phone while driving or, say, to changing whom we're speaking to within the same cell phone call via call waiting-takes its toll on our mental workload. The fact that the audio information we are getting (the conversation) comes from a different direction than the visual information we are seeing (the road ahead) makes it harder for us to process things. Bad reception on the phone? Our struggle to listen more carefully consumes even more effort.

Now replace the gorilla of the basketball experiment with a car making an unexpected turn or a child on a bike standing near the side of the road. How many of us would see it? "Driving's already attention-demanding enough-if you add in the cognitive demands of talking on a cell phone, you're taking away whatever limited resources you had, and you're that much less likely to notice something unexpected," Simons said. "You might be able to stay on the road just fine, and you might be able to stay the same distance behind a car on the highway, but if something unexpected happens-a deer runs into the highway-you might not react as easily."

The notion that we could miss unexpected things while talking on a cell phone is powerfully demonstrated by our seeming failure to notice the expected things. Two psychologists at the University of Utah found, after running a number of subjects through a simulator test, that drivers not talking on a cell phone were able to remember more objects during the course of the drive than those who were. The objects ranged in their "driving relevance" that is, the researchers ranked speed-limit signs and those warning about curves as more critical than Adopt-a-Highway signs. You might suspect that the cell phone drivers were just filtering out irrelevant information, but the study found no correlation between what was important and what was remembered. Most strikingly, the drivers using cell phones looked looked at the same number of objects as the drivers without cell phones-yet they still remembered fewer. at the same number of objects as the drivers without cell phones-yet they still remembered fewer.

Drivers using a cell phone, as noted in the hundred-car study, tend to rigidly lock their eyes ahead, a.s.suming a super-vigilant pose. But that stare may be surprisingly hollow. In a study with an admittedly small sample size, I took the wheel of a 1995 Saturn one day at the Human Performance Laboratory at the University of Ma.s.sachusetts in Amherst, and got set for a virtual drive in the lab's simulator. While I drove down a four-lane highway, a series of sentences was read to me via a hands-free cell phone. My task was to first judge whether the sentences made sense or not (e.g., "The cow jumped over the moon") and then repeat (or "shadow," as researchers call it) the last word in the sentence. As I did this, the direction of my gaze (among other things) was being monitored via an eye-tracking device mounted to a pair of Bono-style sungla.s.ses.

When I later watched a tape of my drive that plotted where my eyes had been looking, the pattern was striking. Under normal driving, my eyes danced around the screen, taking in signs, the speedometer, construction crews in a work zone, the video-game landscape. When I was on the phone, trying to discern whether the sentence made sense, my eyes seemed to train on a point very close to the front of the car-and they barely moved. Technically, I was looking ahead-my eyes were "on the road"-but they were gazing at a place that would not be useful in spotting any hazards coming from the side or even, say, determining whether the truck several hundred feet ahead might be stopping. Which is exactly why I smashed into its rear end. "You were driving like a sixteen-year-old" is how Jeffrey Muttart described it to me.

Our eyes and our attention are a slippery pair. They need each other's help to function, but they do not always share the load equally. Sometimes we send our eyes somewhere and our attention follows; sometimes our attention is already there, waiting for the eyes to catch up. Sometimes our attention does not think that everything our eyes are seeing is worth its time and trouble, and sometimes our eyes rudely interrupt our attention just as it's in the middle of something really interesting. Suffice it to say that what we see, or what we think we see, is not always what we get. "This is the reason the whole 'keep your eyes on the road, your hands upon the wheel, use the hands-free handset' idea is a silly thing," Simons said. "Having your eyes on the road doesn't do any good unless your attention is on the road too."

As with the subjects in the counting test who did not see the gorilla, drivers (and particularly drivers talking on cell phones) would be shocked to learn, later, what they missed-precisely those things the in-car cameras are now revealing. "It is striking that people miss this stuff," Simons said. "At some level it's even more striking how wrong our intuitions are about it. Most people are firmly convinced they would notice if something unexpected happened, and that intuition is just completely wrong."

Human attention, in the best of circ.u.mstances, is a fluid but fragile ent.i.ty, p.r.o.ne to glaring gaps, subtle distortions, and unwelcome interruptions. Beyond a certain threshold, the more that is asked of it, the less well it performs. When this happens in a psychological experiment, it is interesting. When it happens in traffic, it can be fatal.

Objects in Traffic Are More Complicated Than They Appear: How Our Driving Eyes Deceive Us Try to picture, for a moment, the white stripes that divide the lanes on a major highway. How long would you guess they are? How much s.p.a.ce would you say lies between each stripe? When first asked this question, I guessed about five feet, with maybe fifteen feet between the stripes. You might estimate six or even seven feet. While the exact length varies, the U.S. standard calls for ten feet, though depending on the speed limit of the road, the stripes may be as long as twelve or fourteen feet. Take a look at an overhead photo of a highway: In most cases, the stripe is as long as, or longer than, the cars themselves (the average pa.s.senger car is 12.8 feet). The s.p.a.cing between the stripes is based on a standard three-to-one ratio; thus, for a twelve-foot stripe, there will be thirty-six feet between stripes.

I use this as a simple example of how what we see is not always what we get as we move in the unnaturally high speeds of traffic. You may be wondering how it is that humans can even do things like drive cars or fly planes, moving at speeds well beyond that ever experienced in our evolutionary history. As the naturalist Robert Winkler points out, creatures like hawks, whose eyes possess a much faster "flicker fusion rate" than humans', can track small prey from high above as they dive at well over 100 miles per hour. The short answer is that we cheat. We make the driving environment as simple as possible, with smooth, wide roads marked by enormous signs and white lines that are purposely placed far apart to trick us into thinking we are not moving as fast as we are. It is a toddler's view of the world, a landscape of outsized, brightly colored objects and flas.h.i.+ng lights, with harnesses and safety barriers that protect us as we exceed our own underdeveloped capabilities.

What we see while driving is a visually impoverished view of the world. As Stephen Lea, a researcher at the University of Exeter, explains it, what matters is less the speed at which we or other things move than the rate at which images expand on our retinas. So in the same way that we easily observe a person 3 yards away jogging toward us at 6 miles per hour, we have little trouble tracking a car that is 30 yards away moving at 60 miles per hour. The "retinal speed" is the same.

While driving, we get a gently undulating forward view. Things are far away or moving at similar speeds, so they grow slowly in our eyes, until that moment when the car in front suddenly and jarringly "looms" into view (and you notice their b.u.mper sticker: IF YOU CAN READ THIS, YOU'RE TOO CLOSE IF YOU CAN READ THIS, YOU'RE TOO CLOSE). But now picture looking directly down at the road while you're driving at a good speed. It is, of course, a blur. This is no less part of the actual environment in which we are driving, but we are physically unable to see it with any accuracy. Luckily, we do not usually need need to see it to move safely-though, as we shall learn, there are other ways in which traffic puts our visual systems to severe tests. to see it to move safely-though, as we shall learn, there are other ways in which traffic puts our visual systems to severe tests.

Traffic illusions actually hit us before we even get in the car. You may have noticed how in movies or on television, the spokes on a car's wheels sometimes seem to be moving "backward." This so-called wagon-wheel effect happens in movies because they are composed of a flickering set of images (generally twenty-four frames per second), even though we perceive them to be smooth and uninterrupted. Like the dancers in a disco captured briefly by a strobe light, each frame of that movie captures an image of the spokes. If the frequency of the wheel's rotation perfectly matched the flicker rate of the film, the wheel would appear not not to be moving. ("I replaced the headlights in my car with strobe lights," the comedian Steven Wright once joked, "so it looks like I'm the only one moving.") As the wheel moves faster, though, each spoke is "captured" at a different place with each frame (e.g., we may see a spoke at the twelve o'clock position on one sweep, but at eleven forty-five on the next). So it seemingly begins to move backward. to be moving. ("I replaced the headlights in my car with strobe lights," the comedian Steven Wright once joked, "so it looks like I'm the only one moving.") As the wheel moves faster, though, each spoke is "captured" at a different place with each frame (e.g., we may see a spoke at the twelve o'clock position on one sweep, but at eleven forty-five on the next). So it seemingly begins to move backward.

As the cognitive psychologists Dale Purves and Tim Andrews note, however, the wagon-wheel effect can happen in real life as well, under full sunlight, when the "stroboscopic" effect of movies does not apply. The reason we still see the effect, they suggest, is that, as with movies, we perceive the world not as a continuous flow but in a series of discrete and sequential "frames." At a certain point the rotation of the wheel begins to exceed the brain's ability to process it, and as we struggle to catch up, we begin to confuse the current stimulus (i.e., the spoke) in real time with the stimulus in a previous frame. The car wheel is not spinning backward, any more than disco dancers are moving in slow motion. But this effect should provide an early, and cautionary, clue to some of the visual curiosities of the road.

"Motion parallax," one of the most famous highway illusions, puzzled psychologists long before the car arrived. This phenomenon can be most easily glimpsed when you look out the side window of a moving car (though it can happen anywhere). The foreground whizzes past, while trees and other objects farther out seem to move by more slowly, and things far in the distance, like mountains, seem to move in the same direction as us. Obviously, we cannot make the mountains move, no matter how fast we may drive. What's happening is that as we fixate on an object in that landscape, our eyes, to maintain their fixation, must move in a direction opposite to the way we're going. Wherever we fixate in that view, the things we see before the point of fixation are moving quickly across our retina opposite to the direction we are moving in, while things past the point are moving slowly across our retina in the same same direction as we're traveling. (See the notes for a quick demonstration of motion parallax.) direction as we're traveling. (See the notes for a quick demonstration of motion parallax.) All this eye movement and the relative motion of the objects we are seeing, as confusing as it seems, help us judge how far away things are from us. As Mark Nawrot, a psychologist at North Dakota State University and an expert in motion parallax, describes it, this is why film directors like Peter Jackson like to move the camera around a lot. Because we are sitting, stationary, in a theater, and thus cannot get the sort of depth cues our eyes give us when we move, Jackson moves the camera instead, to make the film appear more realistic. But the price we pay for the depth cues that motion parallax provides us is the occasional illusion that we may or may not consciously notice. In traffic, motion parallax may trick us into thinking that an object is far and stationary when, in reality, it is near and moving. near and moving.

The mind can play tricks on what we see, but motion parallax reminds us that what we see while driving plays tricks on our minds. Sense and perception are connected by a quite busy two-way street. The white stripes on the highway and the distance between them are designed precisely as an illusion, to make these high speeds seem comfortable. If both the stripes and the distance between them were short, the experience might feel nauseating. In fact, in some places, engineers have tried to exploit this by employing "illusory pavement markings" to make drivers think they are going faster than they are. In one trial, a series of arrowlike chevrons were painted, ever closer together, on a highway exit ramp. The theory was that as the drivers began to pa.s.s more chevrons for each moment they drove, it would appear as if they were going faster than they really were, and would thus slow down. That study did find that drivers reduced their speed, but in other trials the results have been mixed. Drivers may slow once or twice simply because there are strange markings on the pavement, but they may also quickly acclimate to the markings.

These experiments have been focused on exit ramps because they are a statistically dangerous part of the highway. One crucial reason involves a particular illusion we face in traffic: "speed adaptation." Have you ever noticed, when driving from a rural highway onto a village road with a lower speed limit, how absolutely slow it feels? When you again leave that town to rejoin the rural highway and its higher speed, does the disparity seem as noticeable? The longer we drive at high speeds, the harder it is for us to slow down. Studies have shown that drivers who drove for at least a few minutes at 70 miles per hour drove up to 15 miles per hour faster when they hit a 30-miles-per-hour zone than drivers who had not previously been traveling at the higher speed.

The reason, as Robert Gray, a cognitive psychologist at the University of Arizona, explained to me, is something that might be called the "treadmill effect." After running on a treadmill for a while, you may have noticed that the moment you stop you may briefly experience the sensation of moving backward. As Gray describes it with driving, neurons in the brain that track forward movement begin to become fatigued as a person looking ahead drives at the same speed for a time. The fatigued neurons begin to produce, in essence, a negative "output." When a person stops (or slows), the neurons that track backward motion are still effectively dormant, but the negative output of the forward neurons fools you into thinking you're moving backward-or, if you're changing from high speeds to lower speeds, it can fool you into thinking you have slowed more than you actually have. The illusion cuts both ways, studies suggest: We underestimate underestimate our speed when asked to slow down and our speed when asked to slow down and overestimate overestimate our speed when asked to speed up. This helps explain why we often go too fast coming off a highway (and hence the chevron patterns); it might also explain why drivers entering a highway frequently fail to reach the speed of traffic by the time they're merging (frustrating those in the right-hand lane who are forced to slow). our speed when asked to speed up. This helps explain why we often go too fast coming off a highway (and hence the chevron patterns); it might also explain why drivers entering a highway frequently fail to reach the speed of traffic by the time they're merging (frustrating those in the right-hand lane who are forced to slow).

We misjudge speed in all kinds of ways. Our general perception of how fast and in what direction we are moving-indeed that we are moving at all-comes largely, it is thought, from what has been called "global optical flow." When we drive (or walk), we orient ourselves via a fixed point on the horizon, our "target." As we move, we try to align that target so that it is always the so-called focus of expansion, the nonmoving point from which the visual scenes seem to flow, approaching us in a kind of radial pattern-think of the moment in Star Wars Star Wars when the when the Millennium Falcon Millennium Falcon goes into warp speed and the stars blur into a set of lines streaming away from the center of the s.h.i.+p's trajectory. The "locomotor flow line"-or what you and I would call the road-is the most crucial part of the optic field in driving, and the "textural density" of what pa.s.ses by us influences our sense of speed. Things like roadside trees or walls affect the texture as well, which is why drivers overestimate their speed on tree-lined roads, and why traffic tends to slow between noise-barrier "tunnels" on the highway. The finer the texture, the faster your speed will seem. goes into warp speed and the stars blur into a set of lines streaming away from the center of the s.h.i.+p's trajectory. The "locomotor flow line"-or what you and I would call the road-is the most crucial part of the optic field in driving, and the "textural density" of what pa.s.ses by us influences our sense of speed. Things like roadside trees or walls affect the texture as well, which is why drivers overestimate their speed on tree-lined roads, and why traffic tends to slow between noise-barrier "tunnels" on the highway. The finer the texture, the faster your speed will seem.

The fineness of the road texture is itself affected by the height at which it is viewed. We sense more of the road's optical flow the closer we are to it. When the Boeing 747 was first introduced, as the psychologist Christopher Wickens has noted, pilots seemed to be taxiing too fast, on several occasions even damaging the landing gear. Why? The new c.o.c.kpit was twice as high as the old one, meaning that the pilots were getting half the optical flow at the same speed. They were going faster than they thought they were. This phenomenon occurs on the road as well. Studies have shown that drivers seated at higher eye heights but not shown a speedometer will drive faster than those at lower heights. Drivers in SUVs and pickups, already at a higher risk for rollovers, may put themselves at further risk by going faster than they intend to. Studies have shown, perhaps not surprisingly, that SUV and pickup drivers speed more than others.

The reason we have speedometers, and why you should pay attention to yours, is that drivers often do not have a clue about how fast they're actually traveling-even when they think they do. A study in New Zealand measured the speed of drivers as they pa.s.sed children playing with a ball and waiting to cross the street. When questioned, drivers thought they were going at least 20 kilometers per hour (or about 12 miles per hour) more slowly than they really were (i.e., they thought they were going 18 to 25 miles per hour when they were really doing 31 to 37). Sometimes it seems as if we need someone standing on the side of the road, actually reminding us how fast we are really going. This is why we see "speed trailers," those electronic signs posted by the road that flash your speed. These plaintive appeals to conscience are usually effective, at least in the immediate vicinity, at getting drivers to slow down slightly-but whether drivers want to keep slowing down, day after day, is another issue. The speed trailers work, when they do, because they give us crucial feedback-which, as mentioned in the previous chapter, we so often lack on the road. Some highway agencies, responding to rising numbers of often-fatal rear-end crashes, have tried to put feedback of sorts right on the road, in the form of painted dots that inform drivers of the proper following distances (in one case, someone responded by painting a dot-eating Pac-Man on the highway). Drivers' following distances have tended to increase after dots are put down. Noise also gives feedback: We know we are going faster when the amount of road and wind noise picks up. The faster we go, the louder it gets. But have you ever found yourself listening to the radio at a high volume and then suddenly noticed you were speeding? A variety of studies have shown that when drivers lose auditory cues, they lose track of how fast they're going.

The robot car Junior, as you will recall, did not need to be able to "see" brake lights because he knew exactly how far the car ahead of him was, to within a few meters. For humans, however, distance, like speed, is something we often judge rather imperfectly (hence the Pac-Man dots). Unfortunately for us, driving is really all about distance and speed. Consider a common and hazardous maneuver in driving: overtaking a car on a two-lane road as another approaches in the oncoming lane. When objects like cars are within twenty or thirty feet, we're good at estimating how far away they are, thanks to our binocular vision (and the brain's ability to construct a single 3-D image from the differing 2-D views each eye provides). Beyond that distance, both eyes are seeing the same same view in parallel, and so things get a bit hazy. The farther out we go, the worse it gets: For a car that is twenty feet away, we might be accurate to within a few feet, but when it is three hundred yards away, we might be off by a hundred yards. Considering that it takes about 279 feet for a car traveling at 55 miles per hour to stop (a.s.suming an ideal average reaction time of 1.5 seconds), you can appreciate the problem of overestimating how far away an approaching car is-especially when they're approaching view in parallel, and so things get a bit hazy. The farther out we go, the worse it gets: For a car that is twenty feet away, we might be accurate to within a few feet, but when it is three hundred yards away, we might be off by a hundred yards. Considering that it takes about 279 feet for a car traveling at 55 miles per hour to stop (a.s.suming an ideal average reaction time of 1.5 seconds), you can appreciate the problem of overestimating how far away an approaching car is-especially when they're approaching you you at 55 miles per hour. at 55 miles per hour.

Since we cannot tell exactly how far away the approaching car might be, we guess using spatial cues, like its position relative to a roadside building or the car in front of us. We can also use the size of the oncoming car itself as a guide. We know it is approaching because its size is expanding, or "looming," on our retina.

But there are a few problems with this. The first is that viewing objects straight-on, as with an approaching car, does not provide us with a lot of information. Think of an outfielder catching a fly ball-a seemingly simple act, but one whose exact mechanics still elude scientists (and the occasional outfielder). One thing that's generally agreed upon, as University of Missouri psychology professor Mike Stadler notes, is that b.a.l.l.s are harder to catch when they are hit directly at a fielder. Fielders often have trouble gauging distance and trajectory, and they find they need to move back or forth a bit to get a better picture; studies have shown that fielders have a harder time judging which b.a.l.l.s can or cannot be caught when they are asked to stand still. Viewing a car head-on or directly from behind, as we almost universally do, is like viewing a baseball hit right at you: It doesn't give us a lot to go on.

Another problem is that the image of that car, when it does begin to expand in our eyes, does not do so in a linear, or continuous, way. The book Forensic Aspects of Driver Perception and Response Forensic Aspects of Driver Perception and Response gives this example: A parked car that an approaching driver sees 1,000 feet away will double on the retina by the time the driver is 500 feet away. Sounds about right, no? But it will double again in the next 250 feet, and again in the last 250 feet. It is nonlinear. To put it another way, we can tell the car is getting closer-although this itself may take as much as several seconds-but we have no idea of the rate at which it is getting closer. This difficulty in judging closing distance also makes pa.s.sing the lead car a problem; studies have shown that it is struck in about 10 percent of overtaking crashes. Another way to think about this is to imagine what happens to skydivers. For much of their fall, they have little sense, looking downward, of how fast they are falling-or even that they're falling at all. But suddenly, as the distance to the ground begins to come within the limits of human perception, they experience what is called "ground rush," with the terrain suddenly exploding into their range of view. gives this example: A parked car that an approaching driver sees 1,000 feet away will double on the retina by the time the driver is 500 feet away. Sounds about right, no? But it will double again in the next 250 feet, and again in the last 250 feet. It is nonlinear. To put it another way, we can tell the car is getting closer-although this itself may take as much as several seconds-but we have no idea of the rate at which it is getting closer. This difficulty in judging closing distance also makes pa.s.sing the lead car a problem; studies have shown that it is struck in about 10 percent of overtaking crashes. Another way to think about this is to imagine what happens to skydivers. For much of their fall, they have little sense, looking downward, of how fast they are falling-or even that they're falling at all. But suddenly, as the distance to the ground begins to come within the limits of human perception, they experience what is called "ground rush," with the terrain suddenly exploding into their range of view.

If all this was not enough to worry about, there's also the problem of the oncoming car's speed. speed. A car in the distance approaching at 20 miles per hour makes pa.s.sing easy, but what if it is doing 80 miles per hour? The problem is this: We cannot really tell the difference. Until, that is, the car gets much closer-by which time it might be too late to act on the information. One study that looked at how and when cars decided to pa.s.s other cars on two-lane highways found that they were as likely to attempt a pa.s.s when an oncoming car was approaching at 60 miles per hour as when it was coming at 30 miles per hour. Why? Because when the pa.s.sing maneuver began, the cars were about 1,000 feet apart-too far to tell the speed of the opposing car. At those distances we are not even really sure if the car is coming toward us or not; the fact that it's in the opposite lane, or that we can see its headlights, might be the only giveaway. A car in the distance approaching at 20 miles per hour makes pa.s.sing easy, but what if it is doing 80 miles per hour? The problem is this: We cannot really tell the difference. Until, that is, the car gets much closer-by which time it might be too late to act on the information. One study that looked at how and when cars decided to pa.s.s other cars on two-lane highways found that they were as likely to attempt a pa.s.s when an oncoming car was approaching at 60 miles per hour as when it was coming at 30 miles per hour. Why? Because when the pa.s.sing maneuver began, the cars were about 1,000 feet apart-too far to tell the speed of the opposing car. At those distances we are not even really sure if the car is coming toward us or not; the fact that it's in the opposite lane, or that we can see its headlights, might be the only giveaway.

So at the crucial distance where one must make a decision, the driver has no idea of a key variable: the "closing rate" of the other car. This is why you may have been forced to rather suddenly abandon your attempted pa.s.sing and make either a voluntary or a forced return to your own lane. We "cheat" like this regularly, relying on a car's perceived distance without taking into account its speed. One study, looking at drivers' left turns across oncoming traffic, found that when the speed of approaching cars was doubled, drivers' estimates of the safe "gap" in which they could cross, which you would guess should have also doubled, went up by only 30 percent. These small discrepancies are the stuff of crashes.

Evidence suggests that we are sometimes fooled into thinking things are not as far away as they appear (and not only the approaching objects in our mirrors!). Studies have shown that people think small cars are farther away than they really are, either because we maintain a mental image of a larger car or because there is less of the car to actually see. Large objects, though, also create problems. Researchers have long been puzzled about the relatively high number of drivers killed while crossing railroad tracks-often when visibility was clear and warning signals were in place. It raises an obvious question: How could a driver not see something as large (and as loud) as a train? One answer is that a driver may have crossed the same set of tracks three hundred times in the last year without ever seeing a train, even when the signals were flas.h.i.+ng. Did they simply not expect it on the 301st trip across the tracks? Did they "look but not see"? The influential psychologist and vision expert H. W. Leibowitz, in what has become known as the "Leibowitz hypothesis," offered another possible explanation: biases in the drivers' perceptual systems.

Large objects often seem to move more slowly than small objects. At airports, small private jets seem to go faster than Boeing 767s, even when they are moving at the same speed. Even experienced pilots who are aware of the actual velocities fall for this illusion. The reason, Leibowitz argued, is that there are two different subsystems that influence the ways our eyes move. One system is "reflexive"-we do it without conscious thought-and is triggered by seeing contours. This system helps us continually see things while we ourselves are moving.

We also use, more actively, "pursuit" eye movements. This is how we view moving objects when we are stationary. We can tell how fast something is moving, Leibowitz said, by how much effort it takes this "pursuit" system to see it, and by how much object there is to see. The larger the object, the less our voluntary systems have to work, and the slower the object seems.

How much slower? Judging by a test of the Leibowitz hypothesis done by researchers at the University of California at Berkeley, a lot slower. Subjects looking at a computer screen were asked to estimate the speed of a series of large and small spheres that moved toward them. Despite the presence of stationary posts and lines on the ground that subjects could use as helpful cues to judge speed, the study found that most people still thought a smaller sphere was moving faster-even when a larger sphere was moving 20 miles per hour faster. It was not until a large sphere was moving twice twice as fast as a smaller one that subjects were no longer convinced that the latter was moving faster. as fast as a smaller one that subjects were no longer convinced that the latter was moving faster.

The problem with visual illusions-and it has been argued that all human vision is an illusion-is that we fall for them even when we know they are illusions. Imagine that you are not even aware of your visual shortcomings. This is what happens when we drive at night. We think we can see better than we actually can-and we drive accordingly. We "overdrive" our headlights, moving at speeds that would not allow us to stop in time for something we saw in the range of our lights. Why do we do this? Leibowitz's theory was that when the ambient light goes down, we lose the use of certain eye functions more than we lose others, in a process he called "selective degradation." Our "ambient vision," which happens mostly on the peripheral retina, helps us with things like walking down the sidewalk or staying on the road; this degrades less at night. Because of this, and because the roadside and the center lines are brightly illuminated by our headlights (studies show that we look at these lines much more at night), we essentially think we are seeing all there is to see.

But another element of our vision performs much worse at night, Leibowitz argued: the focal vision of the central retina. This is what we use to identify things, and it is the more conscious part of our vision. Most of the time, there is nothing to see on the road at night except the red taillights of cars, road signs (which we see and remember more at night), the brightly reflective pavement markings, and the section of road just in front of the car that is bathed in the full glow of our headlights.

Yet when a nonilluminated object enters the road-an animal, a stalled car, a piece of debris, or a pedestrian-we cannot see it as well as we might have thought we would based on how well we seem to be seeing everything else. We are blind to our blindness. Remember this the next time you are out walking. Studies have shown that pedestrians think drivers can see them up to twice twice as far away as drivers actually do. According to one expert, if we were to drive at night in a way that ensured we could see every potential hazard in time to stop-what is legally called the "a.s.sured clear distance"-we would have to drive 20 miles per hour. as far away as drivers actually do. According to one expert, if we were to drive at night in a way that ensured we could see every potential hazard in time to stop-what is legally called the "a.s.sured clear distance"-we would have to drive 20 miles per hour.

Another kind of illusion bedevils us in fog. When fog rolls in on a highway, the result is often a huge, multicar chain-reaction crash. An incident that occurred in 1998 near Padua, Italy, involving more than 250 cars (and the death of four people), is an extreme example of a rather common condition. These sorts of events must be due to poor visibility, no? Obviously, it is harder to see in a fog. But the real problem may be that it is even more difficult to see than we think it is. even more difficult to see than we think it is. The reason is that our perception of speed is affected by contrast. The psychologist Stuart Anstis has a clever demonstration of this; he shows that when a pair of boxes-one colored light, the other dark-are moved across a background of black-and-white stripes, the dark box seems to move faster when it crosses the white sections, while the light-colored box appears to go faster as it crosses the black sections. The higher the contrast, the faster the apparent motion, so even though the two boxes are moving at the exact same speed, they look as if they are taking alternating "steps" as they shuffle across the stripes. The reason is that our perception of speed is affected by contrast. The psychologist Stuart Anstis has a clever demonstration of this; he shows that when a pair of boxes-one colored light, the other dark-are moved across a background of black-and-white stripes, the dark box seems to move faster when it crosses the white sections, while the light-colored box appears to go faster as it crosses the black sections. The higher the contrast, the faster the apparent motion, so even though the two boxes are moving at the exact same speed, they look as if they are taking alternating "steps" as they shuffle across the stripes.

In fog, the contrast of cars, not to mention the surrounding landscape, is reduced. Everything around us appears to be moving more slowly than it is, and we we seem to be moving more slowly through the landscape. The idea that we are not aware of this discrepancy is suggested in studies showing that while drivers tend to slightly reduce their speed in foggy conditions, they do not do so by enough to ensure a safe margin-even when special temporary warning signs have been set up. Ironically, drivers may feel more comfortable staying closer to the vehicle ahead of them-so that they do not "lose" them in the fog-but given the perceptual confusion, this is exactly the wrong move. Similar things happen in the whiteout conditions of snow, in which it is not uncommon for drivers to crash into the back of orange-colored snowplow trucks with flas.h.i.+ng lights. The culprit is not a slippery roadway but low contrast. Drivers may see the back of the truck "in time," but as they think it is going faster than it actually is they may not brake accordingly. seem to be moving more slowly through the landscape. The idea that we are not aware of this discrepancy is suggested in studies showing that while drivers tend to slightly reduce their speed in foggy conditions, they do not do so by enough to ensure a safe margin-even when special temporary warning signs have been set up. Ironically, drivers may feel more comfortable staying closer to the vehicle ahead of them-so that they do not "lose" them in the fog-but given the perceptual confusion, this is exactly the wrong move. Similar things happen in the whiteout conditions of snow, in which it is not uncommon for drivers to crash into the back of orange-colored snowplow trucks with flas.h.i.+ng lights. The culprit is not a slippery roadway but low contrast. Drivers may see the back of the truck "in time," but as they think it is going faster than it actually is they may not brake accordingly.

A simple object, present on every car, is a symbol of the complex interplay of what we see and what we think we see on the road: the side rearview mirror. This itself is a curious, and rather overlooked, device. We might think of it as an essential safety feature, but it is unclear to what extent, if any, it has actually reduced the number of crashes. Moreover, studies show that many drivers do not use it during lane changes, the time when it would be most helpful, relying instead on glances over the shoulder. Then there is the issue of exactly what we are seeing when we look in that mirror. Depending on where you are in the world, either both side mirrors or just the pa.s.senger-side one will be convex, or curved outward. Because of the natural blind spots that exist beyond the edges of any car mirror, the decision was made, beginning in the 1980s, to reveal more of the scene at the expense of the driver's ability to correctly judge distance. Better to see a car improperly than to not see it at all. This is why convex mirrors come with a familiar warning: "Objects in mirror are closer than they appear."

But Michael Flannagan, a researcher at the University of Michigan's Transportation Research Inst.i.tute, has argued that something very strange is going on when we look in that mirror. Mirrors of any stripe tend to puzzle us. As a simple experiment, trace the outline of your head in a foggy bathroom mirror. People tend to think they are tracing the actual size, whereas actually it is half. half. The convex side-view mirror presents a particularly distorted and what he calls "impoverished" visual scene, with many of the typical visual cues we use to judge the world rendered more or less invisible. The only thing that reliably indicates distance, Flannagan says, is the retinal size of the image of the car we see. But the size of the car, like the entire "world" depicted, has been shrunk by the convex mirror. The curvature of the mirror means that everything is in essence being drawn closer to the viewer, which is why it is puzzling that things actually look The convex side-view mirror presents a particularly distorted and what he calls "impoverished" visual scene, with many of the typical visual cues we use to judge the world rendered more or less invisible. The only thing that reliably indicates distance, Flannagan says, is the retinal size of the image of the car we see. But the size of the car, like the entire "world" depicted, has been shrunk by the convex mirror. The curvature of the mirror means that everything is in essence being drawn closer to the viewer, which is why it is puzzling that things actually look farther farther away. away.

But it gets trickier still. Researchers can predict, by measuring the viewing angles and the geometry of the mirror, how much the mirror is distorting the image. (This distortion is greater when a driver looks over to the pa.s.senger-side mirror than when he looks at his own, closer mirror; thus, Flannagan notes, it's a bit of a mystery why in the United States we do not allow driver's-side convex mirrors.) In a number of studies, however, Flannagan and his colleagues have found that people's estimates of the distance of objects is not as far off as the models predict they should be. "The vehicle behind you looks less far away than it ought to based on the smallness of the image size, as if people were somehow correcting a bit," he says. "They're not going on just this retinal size; they know something is making them less susceptible to the distortion on paper than they ought to be."

These puzzles led Flannagan and his fellow researchers to a conclusion that might serve as a better warning label for side-view mirrors: "Objects in mirror are more complicated than they appear." The same could be said of driving, as well as our ability to drive, and probably us too. It is all more complicated than it appears. We would do well to drive accordingly.

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Why Ants Don't Get into Traffic Jams (and Humans Do): On Cooperation as a Cure for Congestion Meet the World's Best Commuter: What We Can Learn from Ants, Locusts, and Crickets When insects can follow rules for laneing, why couldn't we the humans?

-road sign in Bangalore, India

You may feel you have the worst commute in the world: the grinding monotony of sitting in congestion, alternately pressing your brake and accelerator like a bored lab monkey angling for a biscuit; the drivers who stymie you with their incompetence; the slow deadening of your psyche caused by the ritual of leaving home forty-five minutes sooner than you would like so you can arrive at work ten minutes later than your boss would like.

And yet, in spite of all this mental and physical anguish, there's at least small consolation awaiting you at the end of your daily slog: Your fellow commuters did not try to eat you.

Consider for a moment the short, brutish life of Anabrus simplex, Anabrus simplex, or the Mormon cricket, so named for the species' devastating attack on Mormon settlers in Utah in the legendary 1848 "cricket war." Huge, miles-long migratory bands of flightless crickets, described as a "black carpet unrolling across the desert," are still a dreaded sight in the American West. They travel many dozens of miles, munching crops and carrion. They heedlessly spill across roads, causing death for themselves and headaches for another traveling species, or the Mormon cricket, so named for the species' devastating attack on Mormon settlers in Utah in the legendary 1848 "cricket war." Huge, miles-long migratory bands of flightless crickets, described as a "black carpet unrolling across the desert," are still a dreaded sight in the American West. They travel many dozens of miles, munching crops and carrion. They heedlessly spill across roads, causing death for themselves and headaches for another traveling species, h.o.m.o sapiens, h.o.m.o sapiens, whose cars may slip on the dense mat of pulsating crickets. "Crickets on Highway" signs have been posted in Idaho. It turns out the insects are actually katydids, but the point is well taken. whose cars may slip on the dense mat of pulsating crickets. "Crickets on Highway" signs have been posted in Idaho. It turns out the insects are actually katydids, but the point is well taken.

Viewed as a scurrying ma.s.s, the Mormon cricket band seems a well-organized, cooperatively driven collective search for food-a perfect swarm designed to ensure its own survival. But when a group of researchers took a closer look at a ma.s.s of Mormon crickets on the move in Idaho in the spring of 2005, they learned that something more complicated was going on. "It looks like this big cooperative behavior," says Iain Couzin, a research fellow at the Collective Animal Behaviour Laboratory in Oxford University's zoology department and a member of the Idaho team. "You can almost imagine it like a group of army ants, sweeping out to find food. But in actual fact we found out it's driven by cannibalism." What looks like cooperation turns out to be extreme compet.i.tion.

Crickets choose food carefully based on their nutritional needs at the moment, and they often find themselves wanting in the protein and salt departments. One of a cricket's best sources for protein and salt, it turns out, is its neighbor. "They're getting hungry and they're trying to eat each other," says Couzin, an affable Scotsman wearing a faded "Death to the Pixies" T-s.h.i.+rt, in his small office. "If you're getting eaten, the best thing for you to do is to try and move away. But if you're also hungry and trying to eat, the best thing to do is move away from others that are trying to eat you, but also to move toward others to try and eat them." For crickets in the back of the pack, crossing over ground that has already been stripped of food by those in the front, another cricket may be the only meal in sight.

This seems a recipe for anarchy, not well-coordinated movement. What is actually happening is an example of the phenomenon known as "emergent behavior," or the formation of complex systems, like cricket bands, that "emerge," often unexpectedly and unpredictably, from the simple interactions of the individuals. Looking at the swarm as a whole, one might not easily see what is driving the movement. Nor could one necessarily predict by studying the local set of rules guiding each cricket's behavior-eat thy neighbor and and avoid being eaten by thy neighbor-that this would all end up as a tight swarm. avoid being eaten by thy neighbor-that this would all end up as a tight swarm.

For complex systems to work the way they do, they need all, or at least a good number, of their component parts to play by the rules. Think of the "wave" at football stadiums, which begins, studies have shown, on the strength of a few dozen people; n.o.body knows, however, how many waves simply died for lack of partic.i.p.ation, or because they tried to go in the "wrong" direction. What if some crickets got tired of avoiding their neighbors' ravenous jaws and decided to leave the swarm? Some of Couzin's colleagues hooked up small radio transmitters to a number of individual crickets, which were then separated from the larger band. Roughly half of those separated were killed by predators within days. Among the radio-tagged crickets kept within the band, none died. So whatever the risk of being eaten by one's neighbors, no matter how stressful and unpleasant the experience, it's still a better option than going solo.

What's remarkable about the formation of these systems is how quickly the rules-and the form of the group-can change. Another insect Couzin has studied, both in the Oxford lab and in the wild in Mauritania, is the desert locust (Schistocerca gregaria). (Schistocerca gregaria). These locusts have two personalities. In their "solitarius" phase, they're harmless. They live rather quietly, in small, scattered groups. "They're shy, cryptic green gra.s.shoppers," Couzin says. But under certain conditions, such as after a drought, these Dr. Jekylls of the insect world, driven into closer contact by the search for food, will turn into a vast brown horde of marauding, "gregarious" Mr. Hydes. The impact is ma.s.sive: Swarming locusts may invade up to 20 percent of Earth's land surface at a time, Couzin says, affecting the livelihood of countless people. Knowing why and how these swarms form might help scientists predict where and when they will form. And so the team a.s.sembled a large group of Oxford-raised locusts, put them in an enclosed s.p.a.ce, and used custom tracking software to follow what was going on. These locusts have two personalities. In their "solitarius" phase, they're harmless. They live rather quietly, in small, scattered groups. "They're shy, cryptic green gra.s.shoppers," Couzin says. But under certain conditions, such as after a drought, these Dr. Jekylls of the insect world, driven into closer contact by the search for food, will turn into a vast brown horde of marauding, "gregarious" Mr. Hydes. The impact is ma.s.sive: Swarming locusts may invade up to 20 percent of Earth's land surface at a time, Couzin says, affecting the livelihood of countless people. Knowing why and how these swarms form might help scientists predict where and when they will form. And so the team a.s.sembled a large group of Oxford-raised locusts, put them in an enclosed s.p.a.ce, and used custom tracking software to follow what was going on.

When there are few locusts, they keep to themselves, marching in different directions, "like particles in a gas," says Couzin. But when forced to come together, whether in a lab or because food has become scarce in the wild, interesting things start to happen. "The smell and sight of other individuals, or the touch on the back leg, causes them to change behavior," Couzin says. "Instead of avoiding one another, they'll start being attracted to each other, and this can cause a sort of cascade." Suddenly, once the locusts reach a "critical density," they will spontaneously start to march in the same direction.

Now what does all this have to do with traffic? you may be asking. The most obvious answer is that what the insects are doing looks a lot like traffic and that what we are doing on the road looks a lot like collective animal behavior. In both cases, simple rules govern the flow of the society, and the cost for violating those rules can be high. (Picture the highway police car or crashes in the role of predator.) Insects, like humans, are compelled to go on the move because they need to survive. Similarly, if we did not need to provide for ourselves, many of us would probably not choose to drive at the very same time everyone else is. Like insects, we have decided that moving in groups-even if most of us are alone in our own cars-makes the most sense. Virtually since traffic congestion began, plans have been put forward to stagger work schedules so that everyone is not on the roads at the same time, but even today, with telecommuting and flextime, traffic congestion persists because having a shared window of time during which we can easily interact with one another still seems the best way to conduct business.

In both insect and human vehicular traffic, large patterns contain all kinds of hidden interactions. A subtle change in these interactions can dramatically affect the whole system. To go back to the comparison between the Late and the Early Merge, if each driver simply adheres to one rule instead of another-merge only at the last moment instead of merge at your earliest opportunity-the merging system changes significantly. Like the pattern of locusts' movement, human traffic movement often tends to change at a point of critical density. In a reversal of the way that locusts go from disorder to order with the addition of a few locusts, with the addition of just a few cars, smoothly flowing traffic can change into a congested mess.

The locust or cricket commuter, by staying within a potentially cannibalistic traffic flow, is, as Couzin suggests, clearly making the best of a bad situation. And in many ways, we act like locusts. Our seeming cooperativeness can s.h.i.+ft to extreme compet.i.tion in the blink of a taillight. Sometimes, we may be those harmless Dr. Jekylls, minding our own business, keeping a safe distance from the car in front. But at a certain point the circ.u.mstances change, and our character changes. We become Mr. Hyde, furiously riding up to the b.u.mper of the person in front of us (i.e., trying to eat them), angry at being tailgated (i.e., trying to avoid being eaten), wis.h.i.+ng we could leave the main flow but knowing it is still probably the best way home. One study, taken from highways in California, showed a regular and predictable increase in the number of calls to a road-rage hotline during evening rush hours. Another study showed that on the same stretch of highway, drivers honked less on the weekend than during the week (even after the researchers adjusted for the difference in the number of cars).

Another creature does things differently, taking the high road in traffic. This is the New World army ant, or Eciton burch.e.l.lii, Eciton burch.e.l.lii, and these insects may just be the world's best commuters. Army ant colonies are like mobile cities, boasting populations that can number over a million. Each dawn, the ants set out to earn their trade. The morning rush hour begins a bit groggily, but it quickly takes shape. "In the morning you have this living ball of ants, up to five feet high, perhaps living in the crevice of a tree," says Couzin, who has studied the ants in Panama. "And then the ants just start swarming out of the nest. Initially, it's like a big amoeboid, just seething bodies of ants. Then after a period of time they seem to start pus.h.i.+ng out in one direction. It's unclear how they choose that direction." and these insects may just be the world's best commuters. Army ant colonies are like mobile cities, boasting populations that can number over a million. Each dawn, the ants set out to earn their trade. The morning rush hour begins a bit groggily, but it quickly takes shape. "In the morning you have this living ball of ants, up to five feet high, perhaps living in the crevice of a tree," says Couzin, who has studied the ants in Panama. "And then the ants just start swarming out of the nest. Initially, it's like a big amoeboid, just seething bodies of ants. Then after a period of time they seem to start pus.h.i.+ng out in one direction. It's unclear how they choose that direction."

As the morning commuters spread out, the earliest ones begin to acquire bits of food, which they immediately bring back to the nest. As other ants continue pus.h.i.+ng into the forest, they create a complex series of trails, all leading back to the nest like branches to a tree trunk. Since the ants are virtually blind, they dot the trails with pheromones, chemicals that function like road signs and white stripes. These trails, which can be quite wide and long, become like superhighways, filled with dense streams of fast-moving commuters. There's just one problem: This is two-way traffic, and the ants returning to the nest are laden down with food. They often move more slowly, and often take up more s.p.a.ce, than the outbound traffic. How do they figure out which stream will go where, who has right-of-way, on "roads" they have only just built?

Interested in the idea that ants may have evolved "rules to optimize the flow of traffic," Couzin, along with a colleague, made a detailed video recording of a section of army ant trail in Panama. The video shows that the ants have quite clearly created a three-lane highway, with a well-defined set of rules: Ants leaving the nest use the outer two lanes, while ants returning get sole possession of the center lane. It is not simply, says Couzin, that the ants are magically sticking to their own chemical-covered separate trails (after all, other types of ants do not form three lanes). Ants are attracted to the highest concentration of chemicals, which is where the highest density of ants tends to be, which happens to be the center lane.

A constant game of chicken ensues, with the outbound ants holding their ground against the returning ants until the last possible moment, then swiftly turning away from the oncoming traffic. There is the occasional collision, but Couzin says the three-lane structure helps minimize the subsequent delay. And ants are loath to waste time. Once finished with the evening commute, home by dusk, the entire colony moves, in the safety of darkness, to a new site, and the next morning the ants repeat the cycle. "These species have evolved for thousands of years under these highly dense traffic circ.u.mstances," says Couzin. "They really are the pinnacle of traffic organization in the actual world."

The secret to the ridiculous efficiency of army ant traffic is that, unlike traveling locusts-and humans-the ants are truly cooperative. "They really want to do what's best for the entire colony," says Couzin. As worker ants are not able to reproduce, they all labor for the queen. "The colony in a sense is the reproductive unit," Couzin explains. "To take a loose a.n.a.logy, it's like the cells in your body, all working together for the benefit of you, to propagate your genes." The progress of each ant is integral to the health of the colony, which is why ant traffic works so well. No one is trying to eat anyone else on the trail, no one's time is more valuable than anyone else's, no one is preventing anyone else from pa.s.sing, and no one is making anyone else wait. When bringing back a piece of food that needs multiple carriers, ants will join in until the group hits what seems to be the right speed. Ants will even use their own bodies to create bridges, making the structure bigger or smaller as traffic flow pa.s.sing over it requires.

What about merging? I ask Couzin later, in the dining room at Balliol College. How are the ants at this difficult task? "There's definitely merging going on," he says with a laugh. "There seems to be something interesting going on at junctions. It's something we'd like to investigate."

Playing G.o.d in Los Angeles Doesn't matter what time it is. It's either bad traffic, peak traffic, or slit-your-wrists traffic.

-The Italian Job (2003) (2003)

"Sorry, the traffic was horrible." These five words rival "How are you?" as the most popular way to begin a conversation in Los Angeles. At times it seems like half the city is waiting for the other half to arrive.

But there is one night when being late simply will not do, when the world-or at least several hundred million inhabitants of it-wants everyone to get to the same place at the same time. This would be Oscar night, when eight hundred or so limousines, ferrying the stars, arrive in a procession at the corner of Hollywood and Highland, depositing their celebrity carriage at the Kodak Theater. On the red carpet, the media volley questions: "How are you feeling?" "Who are you wearing?" But on Oscar night no one ever asks a larger question: How did eight hundred cars get to the same party in a punctual fas.h.i.+on in Los Angeles?

The answer is found in the labyrinthine bas.e.m.e.nt of City Hall in downtown L.A. There, in a dark, climate-controlled room with a wall-sized bank of glowing monitors, each showing strategic shots of intersections across the city, sits the brains of the Los Angeles Department of Transportation's Automated Traffic Surveillance and Control (ATSAC). Traffic centers like this one are essential in many modern cities, and one sees similar setups from Toronto to London (in Mexico City the engineers delightedly showed me footage of speeding drivers giving the finger to automatic speed-limit cameras).

The ATSAC room in Los Angeles would normally be empty on a Sunday, with only the quietly humming computers running the city's traffic lights-ATSAC will even call a human repairperson if a signal breaks down. But since it's Oscar night, an engineer named Kartik Patel has been in the "bunker" since nine a.m., working on the DOT's special Oscar package. Another man lurks at a desk and does not say much. Teams of engineers have also been deployed in the field at strategic intersections. On a desk sits a little statue of Dilbert at a computer, to which someone has attached a label: "ATSAC Operator."

Since the city cannot shut down the entire street network for the Oscars, the limos must be woven through the grid of Los Angeles in a complex orchestration of supply and demand. Normally, this is done by the system's powerful computers, which use a real-time feedback loop to calculate demand. The system knows how many cars are waiting at any major intersection, thanks to the metal-detecting "induction loops" buried in the street (these are revealed by the thin black circles of tar in the asphalt). If at three-thirty p.m. there are suddenly as many cars as there normally would be in the peak period, the computers fire the "peak-period plan." These area-wide plans can change in as little as five minutes. (For a quicker response, they could change with each light cycle, but this might produce overreactions that would mess up the system.) As ATSAC changes the lights at one intersection, it is also plotting future moves, like a traffic version of IBM's chess-playing computer Big Blue. "It's calculating a demand," says Patel. "But it needs to think ahead and say, 'How much time do I need for the next signal?'"

Over time, ATSAC ama.s.ses a profile of how a certain intersection behaves during a given time on a given day. Patel points to a computer screen, which seems to be running a crude version of the game SimCity, with computer renderings of traffic lights and streets but no people. An alert is flas.h.i.+ng at one intersection. "This loop at three-thirty on a Sunday has a certain historical value, for a year's period of time," Patel explains. "Today it's abnormal, because it's not usually that heavy. So it'll flag that as out of the norm and post it up there as a possible incident." It will try to resolve the problem, says Patel, within the "confines of the cycling."

But on this occasion, the engineers want certain traffic flows-those conveying the stars' limos-to perform better than ATSAC would normally permit, without throwing the whole system into disarray. In the late afternoon, with the ceremony drawing near, it becomes apparent just how difficult this is. Harried requests are beginning to come in from field engineers, who are literally standing at intersections. "ATSAC, can you favor Wilc.o.x at Hollywood?" asks a voice, crackling from Patel's walkie-talkie. Patel, on his cell phone, barks: "Man, did you