Traffic

by Tom Vanderbilt

  What seems to gives us the most trouble, apart from our overconfidence and lack of feedback in driving, are the two areas in which Stanley and Junior, Stanford’s clumsy robot drivers, have a decided edge. The first is the way we sense and perceive things. As amazing as this process is, we do not always interpret things correctly. More important, we aren’t always aware of this fact. The second thing that separates us from Stanley and Junior on the road is that we are not driving machines: We cannot keep up a constant level of vigilance. Once we feel we have things under control, we begin to act differently. We look out the window or talk on a cell phone. Much of our trouble, as I will show in the next chapter, comes because of our perceptual limitations, and because we cannot pay attention.

  How Our Eyes and Minds Betray Us on the Road

  Keep Your Mind on the Road:

  Why It’s So Hard to Pay Attention in Traffic

  Any man who can drive safely while kissing a pretty girl is simply not giving the kiss the attention it deserves.

  —Albert Einstein

  Here is a common traffic experience: You are driving, perhaps down a mostly empty highway, perhaps on the quiet streets around your house, when you suddenly find yourself “awake at the wheel.” You realize, with a mixture of wonder and horror, that you cannot remember what you have been doing for the past few moments—nor do you know how long you have been “out.” You may find yourself sitting in your driveway and asking, as the Talking Heads once did, “How did I get here?”

  This phenomenon has been called everything from “highway hypnosis” to the “time-gap experience,” and while it has long puzzled people who study driving, it is still not fully understood. What is known is that it usually happens in fairly monotonous or familiar driving situations. Some scientists suggest that it’s related to drowsiness, and that we may even be taking what are called “microsleeps” at the wheel.

  What is also unclear is how much attention we were actually paying to the road while under the spell of highway hypnosis versus to what extent we have simply forgotten everything that happened during that period. You may have wondered why you did not drift off the side of the road. Perhaps you were lucky; one study that had subjects drive for several (boring) hours in a driving simulator found that the roughly one in five drivers who succumbed to “driving without awareness”—as measured by EEG readings and eye movements—drifted out of their lane one-third of the time. You may have wondered what would have happened if a car (or bike or small child) had veered into the lane while you were zoning out. Would you have responded in time? Did a near accident almost happen during that period, one that you have since forgotten about?

  Think back to the blank stares of drivers monitored by DriveCam. Why is it so hard to pay attention while we are driving? How and why do our eyes and mind betray us on the road?

  Driving, for most of us, is what psychologists call an “overlearned” activity. It is something we’re so well practiced at that we’re able to do it without much conscious thought. That makes our life easier, and it is how we become good at things. Think of an expert tennis player. A serve is a complex maneuver with many different components, but the better we become at it, the less we think of each individual step. This example comes from Barry Kantowitz, a psychologist and “human factors” expert at the University of Michigan; he has spent years studying the safest and most efficient ways for humans to interact with machines, working with everyone from NASA pilots to operators of nuclear power plants. “One of the interesting things about learning and attention is that once something becomes automated, it gets executed in a rapid string of events,” he says. “If you try to pay attention, you screw it up.” This is why, for example, the best hitters in baseball do not necessarily make the best hitting coaches. Coaches need to be able to explain what to do; Charley Lau, the legendary batting coach and author of the classic book The Art of Hitting .300, never actually hit .300 himself.

  The more overlearned an activity becomes, the less cognitive workload it imposes—though studies suggest that even the most mundane activities, like switching gears, never become fully automatic. The task always costs something. Having less workload is, on the one hand, a good thing. If, while driving, we were to really process every potential hazard, carefully analyze every motion and decision, and break down each maneuver into its component parts, we would quickly become overwhelmed. People who bring test subjects into driving simulators find something like this happening. “We’re not going to get a driver to be one hundred percent vigilant to the driving task, because we would all get out of the car sweating,” according to Jeffrey Muttart, a crash investigator and researcher at the University of Massachusetts. “If you see people get out of a driving simulator test, almost the first thing they do is take a deep, cleansing breath. Because I’m frying their brains. This is a ten-minute drive, and they want to try hard to do well.”

  Too little workload has its own problems. We get bored. We get tired. We lapse into highway hypnosis. We may make errors. Anyone who has (like me) put on mismatched socks or run the coffeemaker without adding coffee or water will be aware of this phenomenon. The absolute ease of the activity allows the mind to wander. A classic psychological principle, the Yerkes-Dodson law, posits that the ability to learn is harmed by too little—or too much—“arousal.” This idea applies as well to human performance. Driving in North Dakota is on the low side of the curve, driving in Delhi on the high side. The ideal conditions presumably lie somewhere in between.

  But where? Most driving rarely requires our full workload. So we listen to the radio, look out the window, or, increasingly, talk on the cell phone or read text messages—in the case of one fatal crash in California, the driver may have been operating a laptop computer as he drove. Or we may change the way we drive—we speed up because driving does not seem overly taxing. To the extent that this keeps us in the middle of the Yerkes-Dodson curve, it’s a good thing. But the problem with driving is that we never know for sure when things are going to change very quickly, when that nice empty road—seemingly safe for a cell phone conversation—is going to turn into an obstacle course. We may also be unaware of just how much workload our secondary activity is consuming.

  “Let’s say you’re driving on a straight road. It’s relatively easy. I could ask you to do arithmetic at the same time and it wouldn’t mess up your driving,” Kantowitz said. “If you’re driving on a curved road, especially if it’s sharp curve, that takes more attention if you’re to keep the car operating safely within the lane. If I ask you to do mental arithmetic on a curve you’ll do it more slowly and you’ll screw it up. Or if you do it well you’ll screw up the driving.” A study by a Danish researcher found that those same types of arithmetic problems took longer to do when driving in a village than on a highway.

  This raises another point: Researchers look at how driving is affected when people do other things, but research also shows that secondary tasks suffer as well. We become worse drivers and worse talkers. This is obvious to anyone who has listened to the wandering, interrupted musings of a driver talking on a phone (journalists know that people calling from their cars give terrible interviews). As Kantowitz put it, “There’s no free lunch.”

  “My basic belief after almost forty years of studying this stuff is that people can’t time-share at all,” Kantowitz told me. “You only get the appearance. It’s like speed-reading. You think you can read really fast but your comprehension disappears. You can give the illusion of time-sharing if it’s simple information, but in general we’re not built for time-sharing.” Think of the annoying crawl type found on the bottom of the screen on CNN and other news networks. We are led to believe that this is how people now process information, as if we are suddenly genetically programmed to multitask. Studies have shown, however, that the more information there is on the screen, the less we actually remember.

  The relative ease of most driving lures us into thinking we can get away with doing other things. Indeed, those oth
er things, like listening to the radio, can help when driving itself is threatening to cause fatigue. But we buy into the myth of multitasking with little actual knowledge of how much we can really add in or, as with the television news, how much we are missing. As the inner life of the driver begins to come into focus, it is becoming clear not only that distraction is the single biggest problem on the road but that we have little concept of just how distracted we are.

  In the largest study to date of the way we actually drive today, the Virginia Tech Transportation Institute, working with NHTSA, equipped one hundred cars in the Washington, D.C., and northern Virginia area with cameras, GPS units, and other monitoring devices, and then set about recording a year’s worth of what it calls “pre-crash, naturalistic driving data.” After poring over forty-three thousand hours of data and more than two million miles of driving, the study found that almost 80 percent of crashes and 65 percent of the near crashes involved drivers who were not paying attention to traffic for up to three seconds before the event.

  That period of time is critical. “A total time of two seconds looking away from the forward roadway is when people start to get in trouble,” explained Sheila “Charlie” Klauer, a researcher at VTTI and the study’s project manager. “That’s when they get to the point when they are starting to lose track of what’s going on in front of them.” The two-second window is not technically related to the “two-second rule” for following distance, but the comparison is instructive. The point is that a lot can happen in two seconds—like colliding with the car in front if it came to a stop or slowed—but drivers, lulled by the expectancy that it will not stop, drive as if the world will not have changed when they return their eyes to the road after that two seconds. They drive as if the world is a television show viewed on TiVo that can be paused in real time—one can duck out for a moment, grab a beer from the fridge, and come back to right where they left off without missing a beat. For many of the crashes, Klauer found that “the eye glance happened to be at exactly the wrong time. If they had not chosen to look away at that very second they would have probably been okay.”

  The sources of distraction inside a car have been painstakingly logged by researchers. We know that the average driver adjusts their radio 7.4 times per hour of driving, that their attention is diverted 8.1 times per hour by infants, and that they search for something—sunglasses, breath mints, change for the toll—10.8 times per hour. Research has further revealed just how many times we glance off the road to do these things and how long each glance takes: In general, the average driver looks away from the road for .06 seconds every 3.4 seconds. “On average, radio tuning takes seven glances plus or minus three,” said Linda Angell, a safety researcher at General Motors, in a conference room at the Technical Center in Warren, Michigan. “That’s for an oldish radio. We do better with the modern radio, which zeroes you in on the right region.” Most of these glances, Angell noted, do not take our eyes off the road for longer than 1.5 seconds. But there are exceptions, such as “intense displays”(e.g., lots of features) or looking for a button you have not pressed in a while. The iPod is changing the equation yet again: Studies have shown that scrolling for a particular song takes our eyes off the road for 10 percent longer than simply pausing or skipping a song—plenty of time for something to go wrong.

  Even a succession of very short glances, less than two seconds each, can cause problems. Researchers talk of the “fifteen-second rule,” which indicates the maximum amount of time a driver should spend operating any kind of in-car device, whether navigation or radio, even as they are (at least occasionally) looking at the road. “What we believe is that task time is very important,” Klauer said. “The longer the task time, the more dangerous the task is, and the greater the crash risk.” And so a fifteen-second task might require only short glances at the device, but, Klauer said, “that risk increases every time the driver looks away.”

  The study found that while dialing a cell phone put drivers at a greater crash risk, talking on a cell phone presented only a slightly higher risk than normal driving. “When a driver is talking or listening on their cell phone, at any given moment within that conversation what our odds ratio is telling us is they’re only at a slightly higher crash risk than an alert driver. Statistically speaking, it’s not different,” Klauer said. Does that mean talking on a cell phone is safe? Maybe it’s all that dialing we need to worry about. But the study also found that talking (or listening) on a cell phone was a contributing factor in as many crashes as dialing was. “We think that’s probably true because while dialing is a much more dangerous task while the driver’s doing it, the task is fairly short,” Klauer told me. “But drivers typically talk on their cell phone for a long period of time. Over that long period of time a lot more crashes and near crashes are more apt to occur. That slight increase in crash risk is starting to add up.” As more drivers talk for longer periods, Klauer said, “it’s going to become a lot more dangerous.”

  The reason we talk for a long time on our cell phones is related to the reason we all think we are better drivers than we are, and to the thing that also makes us think we are better drivers on our cell phones than we are: lack of feedback. Cell phone users are not aware of the risk because, by all surface measures, they seem to be driving fine. Traffic affords us these illusions—until it does not, as the hundred-car study showed. “Cell phone conversations are particularly insidious because you don’t notice your bad performance, particularly the cognitive side,” John Lee argues. “So if you’re dialing the phone, you get immediate feedback because you don’t quite stay in the lane, because you’re punching the buttons.” Once the dialing is done, the driver can again look at the road. The weaving stops. They seem to be in control.

  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: Th
ose 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.