Modern life is fraught with risk—fires, floods, earthquakes, petty crimes, murders, airplane crashes or, simply, falls in the bathtub. Most of us worry about these things, at least sometimes. But in most people’s daily life, driving is unquestionably the riskiest activity.

The chance that you’ll die or be seriously injured in a car crash on any given day is, of course, small. But that risk adds up over the years. For Americans ages 4–34, car crashes are the leading cause of death. Think about that: the leading cause. Your lifetime risk of being killed in a car crash is one in 88, three times greater than being the victim of a homicide—and more than 50 times greater than dying in an airplane crash.

For all Americans, car crashes are by far the leading cause of “accidental” death. About 43,000 people are killed and 2.5 million people suffer disabling injuries every year in about 6 million car crashes. But the fact is most of these crashes aren’t accidents—they could have been prevented. You can’t control the way other motorists drive, but you can lower the chances that you’ll be involved in a car crash by avoiding certain types of high-risk driving behavior.

Quantifying Risk

But what counts as risky driving behavior? Certainly, drunk driving—about 40 percent of collisions that result in death are alcohol-related. But apart from that, speeding, drowsy driving, distracted driving and aggressive driving are commonly viewed as being among the most dangerous behaviors. Until recently, however, no one knew exactly how unsafe these four behaviors are.

That’s no longer true. Several years ago, the AAA Foundation for Traffic Safety commissioned the Virginia Tech Transportation Institute (VTTI) to conduct an innovative study of risky driving behaviors (see “How They Did It” below), and, at the end of 2006, VTTI produced a report, How Risky Is It? An Assessment of the Relative Risk of Engaging in Potentially Unsafe Driving Behaviors. Because the study used in-vehicle cameras that examined actual driving behavior, for the first time it was possible to compare what drivers did while driving with their becoming involved in a crash or near-crash. Based on the VTTI report and related studies, here’s what we know about the risks associated with some of our most dangerous driving behaviors:

Speeding nearly triples the risk of being involved in a crash or near-crash. Driving too fast for existing driving conditions reduces your ability to steer safely, extends your stopping distance and can prevent you from reacting quickly enough to avoid a crash.

To make matters worse, relatively small speed increases can have large and possibly lethal consequences because a vehicle’s crash impact increases exponentially with its speed. For example, driving 55 mph versus 50 mph speed limit increases a car’s crash impact by 21 percent, but driving 60 mph versus 50 mph limit increases a vehicle’s impact by 44 percent.

Speeding is probably the single biggest cause of traffic fatalities, according to the Institute of Transport Economics. The report also concluded that a 10 percent reduction in average traffic speed would likely reduce fatal traffic crashes by 34 percent.

Drowsy driving nearly triples the risk of being involved in a crash or near-crash. About half of all adult American drivers surveyed admit to sometimes driving while drowsy, according to a National Sleep Foundation (NSF) poll. What’s more, 37 percent of drivers admitted to having fallen asleep at least once while driving, according to a recent Gallup poll sponsored by the National Highway Traffic Safety Administration (NHTSA). And 51 percent of teens reported driving while drowsy within the previous year, a 2006 NSF poll found.

With numbers like these, it’s not surprising that a recent analysis of U.S. data showed that 4 percent of police-reported crashes involved drowsiness or falling asleep at the wheel as a principal cause. But the actual number of crashes caused by drowsy drivers is probably much higher, because drowsiness is easy for police to overlook as a cause.

Distracted or inattentive driving nearly doubles the risk of being involved in a crash or near-crash. Distracted or inattentive drivers are less likely to be aware of what they need to know to drive safely. In some cases, drivers are completely unaware of important risks; in others, their reaction times are dangerously delayed. (In the VTTI study, instances of distracted or inattentive driving were measured by the number of times that drivers took their eyes off the road for more than two seconds.)

Another AAA Foundation study found that almost all of the studied subjects engaged in distracting activities while driving. Of the hours of driving that researchers observed, drivers were distracted nearly one-third of the time that vehicles were in motion. Conversing with passengers was the most distracting activity (15 percent of the time), eating and drinking was second (5 percent) and reaching for objects or vehicle controls was third (4 percent).

Various studies have shown how dangerous distracted and inattentive driving can be. The most recent, a 2006 NHTSA-funded study of 100 vehicles outfitted with video monitors, found that engaging in nondriving tasks and not watching the road carefully contributed to far more crashes than previously believed—78 percent of crashes and 65 percent of near-crashes.

Of course, some distractions are more perilous than others. For example, the 2006 NHTSA study also showed that cell phones and PDAs were by far the most frequent contributor to dangerous events (644 total), followed by passenger-related inattention (375); internal distractions, such as moving objects around (200); vehicle-related factors, such as fussing with radios and vehicle controls (175); personal hygiene (about 150); and eating (about 150).

Aggressive driving more than doubles the risk of being involved in a crash or near-crash. Aggressive driving can be hard to define, but drivers know it when they see it—rude gestures, verbal abuse, flashing headlights out of annoyance, aggressive tailgating, driving at excessive speeds, unsafe lane changes or deliberately blocking other drivers from changing lanes.

Because aggressive driving is difficult to define, there are few estimates of the number of crashes it causes, and the available estimates we do have are problematic. Representatives from the NHTSA once testified that perhaps two-thirds of all highway deaths were related to aggressive driving. Traffic-safety researchers, however, have been reluctant to set precise percentages.

Surveys of drivers suggest that the problem of aggressive driving is widespread and perhaps growing. A recent poll found that 60 percent of drivers regarded unsafe driving by others as a major threat—even though more than half admitted to occasionally driving aggressively themselves. And sometimes, people don’t see that they’re part of the problem. A British survey found that, while 62 percent of respondents reported having been tailgated aggressively, only 6 percent admitted to aggressive tailgating themselves.

The Bottom Line

Risk is a regular part of American life—whether we’re driving the roads near home or just going for a walk. (Most traffic crashes, it turns out, occur within just a few miles of home.) There’s even risk when we’re shuttered tightly in our houses, where 40 percent of all accidental deaths and disabling injuries occur.

But, for most of us, driving is the most dangerous regular activity, so it’s good to know that we can control a lot of our risk in that arena—and increase our odds of getting to our destination safely. We can decide, for example, to cut our crash risk in half by driving less aggressively or driving with our mind focused fully on the road. Similarly, we can consider whether it’s really worth tripling our risk of a crash by speeding or driving while drowsy.

Some people believe that, one day, car crashes will become almost a thing of the past, as auto manufacturers and highway engineers develop better technology. But those days are a ways off. In the meantime, we can start thinking about whether we really need to answer that cell phone call while we’re driving or take a bite out of that double cheeseburger precariously perched on our passenger seat. After all, that cell phone call might just be a wrong number. And the cheeseburger might still be juicy when we get home—or at least when we get to the next red light. 
 
About the Author

Steven A. Bloch has been a traffic-safety researcher and policy analyst with the Automobile Club of Southern California for the past 25 years. The article originally appeared in the March/April 2008 edition of Westways.

How They Did It

For their study, Virginia Tech Transportation Institute researchers wanted to relate potentially dangerous driving activities (speeding, drowsy driving, distracted driving, aggressive driving) to the problematic outcomes of those activities (police-reported crashes, nonpolice-reported crashes, near-crashes and minor incidents). This comparison, a true measure of “driver’s risk,” had never been done before because it required knowing what was going on at all times inside a large number of vehicles over a lengthy time period. So researchers equipped a series of vehicles with video recorders and sensors that monitored driver actions and reactions, as well as changes in the vehicle’s environment. They also attached electronic devices that detected any sudden vehicle movements. In all, 109 drivers were video-recorded for about a year.

How Risky Is It? An Assessment of the Relative Risk of Engaging in Potentially Unsafe Driving Behaviors is available for download at www.AAAFoundation.org.