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Status Report, Vol. 42, No. 6 | SPECIAL ISSUE: CRASHWORTHINESS OF CONVERTIBLES | May 31, 2007 Subscribe

Death rates aren't higher in convertibles, but a roof still is safer

Contrary to what you might expect, driver death rates in convertibles aren't higher than in hardtop cars. For years their death rates have tracked closely, both on downward trends. The main difference has been more fluctuation in the death rates for convertibles, probably because there are fewer of them on the road. In 2005 convertibles accounted for just less than 4 percent of 1-3-year-old cars registered in the United States, up from less than 1 percent in 1984.

A greater proportion of deaths of convertible drivers occurs in rollover crashes, in which the benefits of a roof are clear. However, the trend for convertibles has vastly improved over time. In 1990 the driver death rate per million registered 1-3-year-old softtops was 72.8 in rollovers, more than twice as high as the death rate of 29.1 in hardtops. By 2005 the convertibles' driver death rate in rollover crashes had plummeted to 19.8, in line with the 20.6 rate for hardtops.

"It's a huge improvement, but it doesn't mean you're safer in a convertible," says Institute president Adrian Lund.

Death rates in convertibles have declined "in part because of safety features like electronic stability control, side airbags, and rollbars," Lund adds. "Convertibles tend to be heavier than comparable hardtops because they have more structural reinforcements, particularly in the undercarriage for better handling on the road and in the sides of the cars to help protect their occupants in side impacts. This added weight helps to make the convertibles more crashworthy."

Convertibles tend to be driven about 10 to 15 percent fewer miles per year than other cars. They also may be driven differently. These factors may help to overstate the crashworthiness of convertibles compared with hardtop cars.

The characteristics of fatally injured drivers of convertibles and hardtop cars differ too. During 2001-05 men accounted for about 7 of every 10 convertible drivers who were killed. This compares with 60 percent of fatally injured hardtop drivers. The convertible drivers tended to be younger — 39 percent were 30-49 years old compared with 25 percent of hardtop drivers in this age group.

The drivers of the convertibles more often were judged to have been speeding, and alcohol use was more prevalent. The fatally injured convertible drivers didn't use safety belts as often as the drivers who were killed in hardtops. This made them more likely to be ejected from their vehicles.

The kinds of fatal crashes also differed. The ones involving convertibles were more likely to be single-vehicle crashes, while those involving hardtop cars more often involved other vehicles.

"What's somewhat surprising is that the safety differences between modern convertibles and hardtops aren't bigger," Lund says. "In part it shows that the auto manufacturers are applying the same crash protection knowhow to their convertible designs, but it's also because convertibles are driven differently — and you have to remember that when you give up the fixed roof of a sedan you give up some protection in crashes. A closed car keeps your arms and head inside the vehicle in a crash, and if you're in a rollover, a roof is always better than no roof."

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