A knife at your throat

The Peltzman Effect has been difficult to prove, given the number of variables that exist both in cars and on the roads, yet experts still joke that the safest cars would be those with unrestrained drivers facing a dagger on the steering column.

In 2007, two university economists turned to what they considered an objective, highly controlled laboratory: NASCAR. After parsing track data from 1972 to 1993, the researchers confirmed the Peltzman Effect. As cars became safer, racers drove more recklessly. Safer cars equaled more crashes.

The total number of injuries also decreased, however, although not by as much if drivers had not compensated with riskier behavior. (In fact, researchers cited a dual benefit to NASCAR, given that crashes increase viewership.)

But everyday drivers don't get prize money. They get auto insurance discounts just for having the safety devices aboard. They get the chance to take more chances another day. And they get a better shot at surviving the accidents that technology can't prevent.

So what happens off the racetrack? Here, too, multiple studies have found that drivers tend to behave in a riskier or more aggressive fashion when they believe themselves better protected -- either with anti-lock brakes, four-wheel drive, studded snow tires or simply larger vehicles.

The Peltzman Effect gone wild

That spells trouble for everyone else, particularly those in small cars that sustain greater damage in a collision with a pickup or SUV.

In a 2008 study at West Virginia University analyzing national fatal-crash data from 1995 through 2006, researchers found that SUVs were 2.7 times more likely to cause an accident than passenger cars.

Click here to become a fan of MSN Money on Facebook

In addition, researchers are now starting to find that semiautomated safety devices, such as those that monitor distance from another vehicle, threaten to breed a dangerous complacency behind the wheel.

"It could be the Peltzman Effect gone wild," says Janos Wimpffen, the owner of Sports Car Racing Research Associates, a transportation consultancy.

"If everyone had fairly fragile, small cars, it's likely that their driving behavior would be somewhat more defensive. They would understand that were they to get into an accident, the consequences would be more severe," Wimpffen says. "The opposite of that is people who have very big cars may take greater risks."

More from CarInsurance.com: