Automotive | July/August 2008

Understanding-and changing-risky driving behaviors could reduce the amount of carnage on our highways

By Steven A. Bloch

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 lives, 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 motor vehicle 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 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. 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 to conduct an innovative study of risky driving behaviors, 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. 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 increases a car's crash impact by 21 percent, but driving 60 mph versus 50 mph increases a vehicle's impact by 44 percent.

Speeding is probably the single biggest cause of traffic fatalities, according to a 2004 Institute of Transport Economics report. 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. 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.

A 2003 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 non-driving 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, 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.

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, and pedestrians are involved in one in six California traffic fatalities.) 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.

On the road, we can start thinking about whether we really need to answer that cell phone or take a bite out of a double cheeseburger while we're driving. 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.

Steven A. Bloch has been a traffic-safety researcher and policy analyst with AAA for the past 25 years.