The Frontal Cortex

When cars are stocked with airbags in every possible direction - are there ceiling airbags yet? - drivers become more aggressive:

A Purdue University research team that studied five years of motor vehicle accidents in Washington State concludes antilock brakes and airbags don't minimize accidents or injuries because those systems may encourage riskier driving.

Fred Mannering, a Purdue professor of civil engineering, led the study. The results, which are bound to be controversial with auto makers and safety experts, say the innovations designed to improve safety also make drivers less vigilant.

Mannering calls this behavior "offset hypotheses."

He notes that when ABS debuted, insurance companies said accident rates actually increased for vehicles equipped with the systems that prevent wheels from locking up while braking.

His team analyzed accident data from Washington over a 5-year period beginning in 1992.

"Our findings suggest the offset hypothesis is occurring and that it is sufficient to counter the modest technological benefits of airbags and antilock brakes," Mannering concludes. Using accident data and actual driving records, the researchers calculated the probability of being involved in an accident for drivers of different ages and demographics. Mannering says the research models indicate ABS and airbags do not affect the probability of an accident or suffering an injury.

While this study is interesting - people are clearly willing to engage in more risk within an environment that appears safer - I'd feel better about the conclusions if the researchers controlled for other variables, like horsepower. After all, cars with multiple airbags tend to be more expensive, which means they also have bigger engines. Plus, the timespan of the study coincided with the birth of the SUV craze, when every minivan driver suddenly began buying hulking Suburbans.

And I'm still not sure what we can do to remedy this effect. We can't lie to drivers about the safety features of their car, or convince them that their Volvo is really a combustible Pinto. I'm sure wearing seatbelts also makes us less risk averse, but it's not like anybody wants to go without seatbelts. If airbags are effective - and not everybody is convinced that they are - then we'll just have to deal with a few more bad drivers.