Safer cars, not better drivers, behind fewer roadway deaths

The designs of passenger vehicles have been improving for years, becoming more protective of their occupants in crashes. Without those improvements, the motor vehicle death rate per registered vehicle would have stopped declining in 1994 and started going up, according to a study by the Insurance Institute for Highway Safety.

“Death rates per vehicle and per mile have been going down for decades, and they still are. This study shows why,” said Institute President Adrian Lund.

“In recent years, it’s the vehicles, not better drivers or improved roadways. The study reveals not only the importance of the vehicle design changes and the kinds of vehicles motorists are choosing to drive but, on the downside, the loss of momentum for effective traffic safety policies on belt use, alcohol-impaired driving and speeding.”

The researchers separated vehicle effects from other effects on motor vehicle death rates during 1985-2004 by estimating what the death rate trend would have been if vehicle designs had not changed over the years — that is, if people still were driving the kinds of vehicles they drove in 1985. The death rate trend given that hypothetical vehicle fleet started to go up in the 1990s, which is very different from the actual downward trend during the past 10 years.

“This suggests that an increasingly dangerous traffic environment has been offset since 1994 only because people are driving vehicles that are more protective,” Lund said. “Of course the vehicle design changes are good, but people shouldn’t have to buy new, more crashworthy vehicles to maintain their safety.”

Lund said efforts in the 1980s to mandate belt use and toughen drunk driving laws diminished in the 1990s at the same time states were raising speed limits. “This produced an increasingly dangerous traffic environment,” he said.

An estimated 5,200 additional lives would have been lost in 2004 without the vehicle design changes, he said.

The research report, “Trends over time in the risk of driver death: what if vehicle designs had not improved?” by C.M. Farmer and A.K. Lund will be published in the journal Traffic Injury Prevention, later this year.