It's no secret that teen drivers are at greater risk for accidents than older adults — four times greater, according to the Insurance Institute for Highway Safety. Chalk it up to a number of factors, among them inexperience dealing with emergency situations, distracted driving and the inclination to show off to friends.

Being Distracted Behind the Wheel

Cell phones, CDs, food and even text messages can pose serious distractions to drivers. In some cases, drivers will even text their backseat passengers.

In January, a national survey by the Children's Hospital of Philadelphia and State Farm Insurance reported that 89 percent of teens said they observed other teens driving and talking on their cell phones, and nearly half admitted to doing the same. More troubling is that 53 percent said they observed their peers using handheld devices, like iPods or text-messaging phones, while behind the wheel.

Any form of distraction increases the risk of accident. In 2006, a yearlong study by Virginia Tech observed 241 Washington, D.C., drivers and concluded that distracted driving contributed to 80 percent of collisions. In rear-end accidents, 93 percent of drivers had looked away from the road at some point during the 3 seconds before impact.

Taking Too Many Risks

Actions like ignoring traffic signals or school zone signs and changing lanes without checking blind spots "risky behavior." They said the difference between risky behavior and distracted driving is that risky behavior is deliberate, while distracted driving is often the result of ignorance.

Teenage minds might actually be predisposed to risk-taking. In 2005 and 2006, researchers at Cornell and Stanford conducted risk-reward studies across a range of age groups. The study, funded by the National Institute on Drug Abuse and published in The Journal of Neuroscience, measured activity in two areas of the brain — one that triggers impulsive actions and another that reins them in with rationality and caution. Researchers found that when confronted with risky choices, teen brains exhibit twice as much activity in the impulse area as adult brains, while the area that expresses restraint lags behind. It takes until the early 20s for the two areas to reach parity, the study said.

Speeding

Most drivers occasionally speed, but teens do so because they don't have a good sense of how a car's speed can affect their response time.

"They will exceed speeds on residential roads that they interpret as empty because they haven't had close calls or someone coming out into the road," Tsifrin said.

A 2005 study by the National Institutes of Health in Washington, D.C., found that teens drive an average of 1.3 mph faster than all drivers as a whole. In turn, IIHS reported that speeding factored into roughly one-third of all fatal crashes in 2005 when teenagers were behind the wheel — some 50 percent more than it did in fatal crashes for 20- to 49-year-olds.

Overcrowding the Car

Teens frequently overcrowd their cars, cramming five or six into a cabin meant to seat four or five, Tsifrin said. Worse yet, the extra passengers often result in teens driving more aggressively. The NIH study found that when accompanied by male passengers in the front seat, teens of both genders speed more and leave shorter following distances; a quarter of the drivers in the study broke the speed limit by 15 mph or more. Researchers confirmed the same trend for teenage girls driving with other girls, but teenage boys drove less aggressively when girls rode up front.

The distractions of carrying too many passengers can have serious consequences. A 2000 study by IIHS and the Johns Hopkins University said that with two passengers, 16-year-old drivers were at nearly double the risk of having a fatal accident than if they were driving alone. With three or more passengers, the risk was nearly triple.

Driving Under the Influence

In 2006, a study by the University of Michigan and NIDA reported that 45 percent of high school seniors surveyed said they drank alcohol in the past month. When teens drink and drive, they're even less likely to practice safe habits like seat belt usage: Of the 15- to 20-year-olds killed after drinking and driving in 2003, 74 percent were unrestrained, according to the National Highway Traffic Safety Administration.

"This is a huge problem," Tsifrin said. "Because they're too young to drink legally ... they're also less likely to call their parents to come and get them. It's more likely for a 22-year-old to call their parents and tell them to pick them up."

Of course, alcohol isn't the only influence: Last January's State Farm/CHOP survey said that 45 percent of teens reported seeing other teens drive high. A study in 1999 by NHTSA and Maastricht University in the Netherlands found that after low doses of marijuana, reaction times worsened by 0.9 seconds when moving at 59 mph in test conditions. That translates to an extra 78 feet of travel. With both alcohol and marijuana, reaction times were 1.6 seconds, or 139 feet, worse.

Following Too Closely

At 60 mph, a typical car needs between 120 and 140 feet to reach a full stop. Most SUVs require an extra 5 to 10 feet on top of that. Consider that 60 mph translates to 88 feet per second, and it's easy to see why maintaining a proper following distance is a critical step in preventing accidents. Unfortunately, many teens fail to do so: In the NIH study, teen drivers left nearly two-tenths of a second less following distance behind the car ahead than did general traffic. Even at 40 mph, that's 10 feet less stopping distance.

Tsifrin blames it on driving tactics that flaunt swagger over safety. "They want to drive aggressively as far as showing off," he said. "There's still the kind of high school attitude of 'Who am I in the pecking order?'"

Driving Unbuckled

A 2003 survey by NHTSA reported that 79 percent of drivers age 16 to 24 said they wore their seat belts regularly, while 84 percent of the overall population did so.

Tsifrin blames the lack of usage on many young drivers' sense of invincibility — "the hubris of youth," he called it — which also factors into teen speeding. Fortunately, many cars today have seat belt reminders that flash warning lights or chime until belts are secured. Call them annoying, but they help keep occupants buckled.

Not Being Able to Handle Emergencies

Knowing how to avoid an accident comes with driving experience. Young drivers can only learn so much in the classroom, which leaves learning maneuvers like straightening out a skid or how to apply the brakes correctly to real-world experience. Speeding and distracted driving only make things worse, Tsifirn said, as they compound the lack of experience by putting drivers at higher risk of encountering an emergency situation in the first place.

Driving Drowsy

Drowsy driving affects an unlikely group — the so-called "good kids," Tsifrin said. That means straight-A students or those with a full plate of extracurricular activities.

"Overachievers have a lot of pressure here," he said. "If they're playing varsity sports and are also preparing for an AP English exam, and if they've been going from 7 a.m. and now it's midnight and they have to get home, they don't think, 'I'm too tired to drive.'"

Fatigue can affect more than just the valedictorians and star athletes. Three-fourths of teens in the State Farm/CHOP survey said they had observed their peers driving while fatigued. Across the general population, NHTSA estimates that fatigue and sleep deprivation contribute to some 100,000 reported crashes and 1,500 deaths each year.

Choosing the Wrong Car and Not Maintaining It

Too often, a combination of tight budgets and high style leads teens to pass up important safety features for larger engines and flashy accessories.

"A teen or novice driver ... will opt for a cool-looking sports car rather than a car that's really a safer choice," Tsifrin said. "Then, if they sink all their money into it, they might be remiss in maintaining it."

That doesn't just mean forgetting to check tire pressure or picking a car with a sunroof instead of one with antilock brakes. It can also translate into buying oversized SUV wheels that look fancy but reduce highway stability, or getting a performance stereo that drowns out potential hazards a driver might hear, such as an ambulance siren.