Traffic (12 page)

Drivers may confidently assume they can adequately compensate for talking on a cell phone or texting on a BlackBerry by lowering their speed or putting more space between their own car and the car ahead of them, but the evidence gleaned from the hundred-car survey suggests otherwise. One might think, for example, that rear-end collisions most commonly occur because the driver behind was following too closely. Yet the study found that the majority of rear-end crashes happened when the following car was
more
than two seconds away from the car it struck. “I think people compensated a little bit for their inattention,” Klauer said. “‘I need to answer this cell phone, I need to look at these papers on the seat next to me.’ So they back off the lead vehicle and give themselves some space. Then they start to engage in something else. Then something unexpected happens and they’re in trouble.”

The drivers were redistributing workload. With more of their attention devoted to a cell phone conversation, they may have had to work just a bit harder to stay in their lane; similarly, the narrower the lane, the more mental energy it takes to stay in that lane (my own theory is that cell phones in cars have contributed to the seeming death of signaling for turns). Driving closer to someone also requires more mental energy, as does driving fast. We can usually feel this starting to take a toll, so we do things like drop back from a car in front of us or slow down. Clearly we do not always compensate enough, and there is evidence to suggest that we hardly compensate at all for our cell phone impairment when we’re doing things like changing lanes.

Something similar happens with very new drivers on highways: So much of their mental concentration is devoted to simply staying in the lane, they have trouble paying attention to their speed. And it is not only drivers who suffer, as anyone who has walked behind someone talking on a mobile phone has noticed. When psychologists have asked people to walk around a track while memorizing words that were shown to them, walking speeds slowed as the mental task got harder. Similarly, researchers in Finland have found that pedestrians using mobile devices walked more slowly
and
were less able to interact with the device, pausing occasionally to “sample the environment.” But pedestrians on cell phones do not sample the environment as often as they should, as a study of a Las Vegas crosswalk showed: Those talking on cell phones were less likely to look at traffic while crossing
and
took longer to do so.

Our attention, like a highway dropping from three lanes to two lanes, suffers from a bottleneck, one theory claims: Only so much can get through at once. Trying to squeeze more mental “cars” past the bottleneck means we have to slow them all down, space them out—or it means that some of those cars might drive off the road. In the hundred-car study, something else was also happening when drivers got on their cell phones. They began to look almost exclusively straight ahead, much more so than they did when they were not on their cell phones. They were, by external measures, “paying attention.” But keeping one’s eyes on the road is not necessarily the same thing as keeping one’s mind on the road.

Consider for a moment the incredibly complex question of what it even means to pay attention while driving. There are an infinite number of things we could notice if we chose to, or had the spare mental capacity. But through practice and habit we learn to expertly analyze complicated scenes and extract only the information we need, ignoring the rest. New drivers, as we have seen, look rather rigidly ahead and near the front of the car, using “foveal” rather than peripheral vision to help them stay in their lane. As drivers get more experienced, they cast their eyes farther out along the road, barely registering the pavement markings. This happens without their even noticing. Experiments have been done in which researchers pulled over drivers on the highway and asked them if they recalled having seen certain traffic signs. The recall rates were as low as 20 percent. Were drivers simply not seeing things? One study found that the remembered signs were not necessarily the most visible ones but the signs that drivers judged most important (e.g., speed limit). This suggests that drivers saw enough of the signs to process what they were, at some subconscious level, and then effectively forgot most of them.

We do this sort of thing all the time—and for good reason. Remembering traffic signs we have seen is not useful to our lives. Steven Most, a psychologist at the University of Delaware, compares the flow of information and images we get in daily life to a stream passing through our heads. Unless we stop to “scoop up” some of that water—or “capture” it with our attention—it will flow in and out of our minds. “Sometimes, you attend to things enough to be aware of them in the moment, but that encoding process isn’t necessarily taking place,” he told me. “The awareness is there but not the memory of the awareness. When attention is distracted enough, it’s even questionable whether we have that momentary awareness.”

The reason we notice things like signs while driving is not as simple as it might seem. The average driver, asked why he saw a stop sign, might say, “Because it was there” or “Because it’s the color red, and humans are hard-wired to see red more easily.” But often we see a sign simply because we know where to look for one. This curious fact was explained by Carl Andersen, a vision specialist with the Federal Highway Administration, in a laboratory filled with eye-catching prototype warning signs in bold new colors like “incident pink.” “If drivers are in an area that they already know, they almost don’t even see the sign, because they already know it’s there,” Andersen said. This is known as “top-down processing.” We see something because we are looking for it. To see things that we are
not
looking for, like unexpected stop signs, we need to rely on “bottom-up processing.” Something has to be conspicuous enough to catch our attention. “If you’re on one of those divided state highways, the older highways, you’re not expecting to stop,” Andersen said. “You’d better have advance signing and reduce the speed to prepare people for it.”

Drivers actually look at most traffic signs at least twice: once for “acquisition” and again for “confirmation.” Curiously, we do not really read things like stop signs. “Studies have been done where they intentionally misspell ‘stop,’” Andersen said. “Everybody stops and then they drive off. They query the people later and the vast majority never saw that it was misspelled.” (In fact, they may not have even seen it; it’s estimated that one-fifth of our viewing time is interrupted by blinks and what are known as saccades, or our eyes’ rapid movements, during which we are, as one expert puts it, “effectively blind.”) Other studies, in driving simulators, have done things like change “No Parking” signs briefly to stop signs, and then back again. When the signs were at intersections, where stop signs usually are, drivers were more likely to notice the change. When they popped up elsewhere (e.g., at mid-block), drivers hardly ever noticed the change. When the drivers did see the sign change from “No Parking” to “Stop” at the intersection, they did not see it change back to “No Parking.” Their decision to stop, the researchers noted, had already been made.

What does this have to do with real driving? After all, traffic signs do not change capriciously. A lot of things in traffic
do
change, however, and the question of whether we will notice those things depends not just on how visible they are but, indeed, on whether or not we are looking for them and how much spare capacity we have to process them. In a now-famous psychological experiment, a group of researchers had subjects view a video that showed a circle of people passing a basketball around. Half wore white shirts, half wore black. The subjects were asked to count the number of passes. What at least half the subjects did not notice was that a person wearing a gorilla suit passed right through the middle of the circle of basketball players. They were suffering from what has been called “inattentional blindness.”

The idea that people could not see something as striking as a gorilla in a group of basketball players, although their eyes were locked on the video screen, suggests just how unstable and selective attention is—even when we are giving something our “undivided” attention. “There’s an unlimited amount of information in the world, but our capacity for attending to information is pretty limited,” explained Daniel Simons, a psychologist at the University of Illinois and the coauthor of the gorilla study. “If you’re limited in how many things you can pay attention to, and attention is a gateway to consciousness, then you can only be aware of a limited subset of what’s out there.”

Inattentional blindness, it has been suggested, is behind an entire category of crashes in traffic, those known as “looked but did not see accidents.” As with the gorilla-experiment subjects, drivers were looking directly at a scene but somehow missed a vital part—perhaps because they were looking for something else, or perhaps because something came along that they were
not
looking for. All too often, for instance, cars collide with motorcycles. One of the most frequently cited reasons is “failure to see,” and these events are so common that motorcyclists in England have taken to calling them SMIDSYs, for “Sorry, Mate, I Didn’t See You.”

Many people assume that “failure to see” means that the motorcycle itself was difficult to see, because of its size or its single headlight. But it may also be that car drivers tend to be on the lookout for other cars when entering an intersection or turning across a lane of oncoming traffic. They may be in a sense “looking through” the motorcycle, because it does not fit their mental picture of the things they think they should be seeing. This is why safety campaigns (e.g., “Watch for motorcycles” or the United Kingdom’s “Take longer to look for bikes”) stress the idea of drivers simply being aware that motorcycles are out on the road. “The common intuition is that we first see things in the world and then interpret the scene in front of us,” said Most. “What this work shows is that it’s possible that the idea you have in mind actually precedes the perception and affects what you see. Our expectations and knowledge of what’s in a scene influence what we see in a scene.”

These expectations might also help explain the troublingly high numbers of emergency vehicles that are struck on the highway, even as they sit on the shoulder with their lights flashing brightly (and despite the fact that most places have laws requiring drivers to change lanes or slow down in the presence of an ambulance). These incidents are so common that the term “moth effect” has been coined for them. The idea is that drivers are lured to the lights, like moths to a flame.

What could cause a moth effect? There are many theories, ranging from arguments that we tend to steer where we look (which raises the question of why we do not drive off the road every time we see something interesting) to the idea that humans instinctively look toward light (ditto). Other researchers have argued that the fixation of attention on the roadside leaves drivers less able to judge their position in the lane. Many moth effect crashes involve alcohol-impaired drivers, perhaps no surprise in light of work that suggests that alcohol has a particularly deleterious effect on our eyes’ ability to perceive depth or direction while we are moving.

The simplest explanation may be that most drivers, upon seeing a car on the highway, assume that it is moving at the same high speed as everyone else—and cars with flashing lights are usually moving even
faster
than that. One study, conducted in a driving simulator, showed that drivers reacted more quickly when stopped police cars were parked at an angle to oncoming traffic, rather than straight ahead in the direction of traffic. As the two vehicles were essentially equally conspicuous, the reason the angled car was seen sooner had less to do with visibility than in how the drivers interpreted what they saw: a car that was obviously not moving in the direction of traffic. (This ability to interpret seemed to be a by-product of driving experience, as novice drivers had the same reaction times for both cars.)

Even when we see an unexpected hazard, the fact that it’s outside our “attentional set” means we are slower to react to it. This is demonstrated in a classic psychological test for what is known as the “Stroop effect.” Subjects are shown a list of color names; these words are printed in the same color as the name as well as in other colors. Naming the color a word is printed in, it turns out, typically takes longer when the word does not match the color; that is, it takes longer to say “red” when the word printed in red is “yellow” than when it’s “red.” One argument for why this happens is that while reading is for us an “automatic” activity, naming colors is not. The automatic gets in the way of the less automatic (as with the stereotyping studies in Chapter 1). But other theories suggest that attention is involved. That we can name the correct color when the word itself is “wrong” suggests that we can train our attention on certain things; yet the fact that it takes us longer to do it shows that we cannot always screen out the things on which we are not focused (i.e., the word itself).

What this means for traffic was highlighted in a study by Most and his colleague Robert Astur. Drivers on a computer driving simulator, navigating through an ersatz urban environment, were asked to look for an arrow at every intersection telling them where to turn. For some drivers, the arrow was yellow and for others it was blue. At one intersection, an approaching motorcycle, itself either blue or yellow, suddenly veered in front of the driver and stopped. Drivers’ reaction times to slam on the brakes were slower—and their collision rates were higher—when the motorcycle was a different color than the arrow. In a purely bottom-up form of processing, we might expect the motorcycle to stand out because it is different; but because we are looking at the scene from a top-down perspective, the odd-colored motorcycle is less visible because it is different from those things for which we are searching.

This attention disorder could also help explain the “safety in numbers” phenomenon of traffic, as described by Peter Lyndon Jacobsen, a public-health consultant in California. You might think that as there are more pedestrians or cyclists on a street, the more chances there are for them to be hit. You are right. More pedestrians are killed by cars in New York City than anywhere else in the United States. But as Jacobsen found, these relationships are not linear. In other words, as the number of pedestrians or cyclists increases, the fatality rates per capita begin to drop. The reason, as Jacobsen points out, is not that pedestrians begin to act more safely when surrounded by more fellow pedestrians—in fact, in New York City, as a stroll down Fifth Avenue will reveal, the opposite is true. It is the behavior of
drivers
that changes. They are suddenly seeing pedestrians everywhere. The more they see, typically, the slower they drive; and, in a neatly perpetuating cycle, the more slowly they drive, the more pedestrians they effectually see because those pedestrians stay within sight for a longer period.