Like a lot of consumers, Paul McAleer focused on comfort when he recently went car shopping. Adjustable seats, a tilt steering wheel and extra height were all important.
Because he's a self-described "fat guy," the Web site designer also has to check to see if he can fit in the seat belt.
While McAleer buckles up when he drives, a new study found that seat belt use declines as body size increases. But even large drivers who want to use a seat belt may be thwarted because not all carmakers offer bigger belts or extenders.
"It would be in their best interest to make seat belts longer in the first place," says McAleer, who lives in Chicago.
Federal standards that specify the length of auto seat belts date back four decades and only require that seat belts accommodate a 215-pound man. Some manufacturers offer bigger belts or extenders anyway, but other auto companies have concerns about effectiveness and liability.
Vanderbilt University psychologist David Schlundt studied the relationship between seat belt use and weight after noticing that obese people sometimes struggled to fit into the auto restraints.
"They really have a hard time getting that belt buckle over them," Schlundt said. "They have to stretch it out and then over and then some can't see the buckle."
Schlundt and his colleagues at Meharry Medical College in Nashville reviewed nearly 250,000 responses about seat belt use from a national telephone health survey by the U.S. Centers for Disease Control and Prevention.
Based on that 2002 data, the study found that seat belt use declined as body mass index — a calculation based on height and weight — increased.
Only about 70 percent of extremely obese individuals reported always using a seat belt, while nearly 83 percent of normal-weight people always used their belts, the study found. More than half of those killed in auto accidents weren't wearing seat belts, according to the latest federal figures. The study's findings were published in the journal Obesity.
"I hate seat belts because they always seem to ride up and strangle me," said Peggy Howell, the public relations director for the National Association to Advance Fat Acceptance. "But I wear them for my own safety and because it is the law."
Howell said people sometimes contact her Oakland, Calif.-based advocacy group to get information on extensions.
McAleer, who runs a Web site called Big Fat Blog, said he's worried the study will focus criticism on the obese instead of the design of seat belts. His new car has seat belts long enough for him, but he said his wife has a harder time buckling up.
Many factors affect seat belt use, including sex, age and state laws, but Schlundt said the connection between increased weight and decreased use was consistent when those things were taken into account.
Government regulations for auto manufacturers don't use BMI to determine dimensions for seat belts. The standard instead says belts must fit up to a 215-pound man who has a seated hip circumference of 47 inches. That was set in the 1960s.
When the National Highway Traffic Safety Administration considered changing the rules in 2003, it estimated that more than 38 million people, or 19 percent of the total U.S. population, were larger than the seat belt requirements.
The NHTSA decided not to revise its standards since most top manufacturers including Ford Motor Co., General Motors Corp., Chrysler LLC, Nissan Motor Co. and Honda Motor Co. have seat belts that are longer than required.
The companies each provide an average of 18-20 inches of extra belt length, more than enough to accommodate the largest percentage of drivers. Many of those manufacturers also have seat belt extensions or longer belts that can be purchased or installed at dealerships. Ford offers their extensions for free, said Wes Sherwood, a Ford spokesman.
Several foreign brands, such as Honda, BMW, Hyundai, Mercedes-Benz and Porsche, do not provide seat belt extenders. Ford's Volvo division requires buyers to sign a waiver stating they've read a list of warnings and rules for using extenders, said Daniel Johnston, a Volvo spokesman.
Extensions have to be used carefully because they can be hazardous if used by passengers who are too small, said Phil Haseltine, president of the Washington, D.C.-based Automotive Coalition for Traffic Safety.
According to the NHTSA, an incorrectly sized seat belt extender could fail to provide upper body restraint and may pull the lap belt onto the abdomen during a front impact, possibly leading to internal injury.