As Americans grow heftier, automakers are making seats wider, adding more space to interiors and using bigger virtual mannequins to help design vehicles.

Domestic automakers say they already had seats for increasingly rotund motorists. Now foreign brands are catching up.

Getting bigger:

– Honda. The 2006 Civic offers front seats that are three-quarters of an inch wider than those in the 2005 model. Purpose: "To meet the growing needs of our customers," spokesman Sage Marie says.

– Mercedes-Benz. The big R-Class Grand Sports Tourer, which went on sale at the end of September, has front seats about a half-inch wider than the smaller Mercedes M-Class crossover.

– Subaru. The first-ever B9 Tribeca, a crossover vehicle introduced this year that was specifically designed for the U.S. market, has front seats a half-inch wider than those in the Legacy, the next-largest wagon in the lineup.

– Mitsubishi. The Lancer Evolution was given front seats slightly wider than in the Japanese version when the performance car was introduced in the USA in 2003.

Extra-wide seats are important now that 62 percent of adults are considered overweight or obese, according to market research firm NPD Group. The figure has doubled since the late 1970s.

For the auto industry, the solution is not just about hippy seats. It’s also wider cars.

Toyota added a half-inch of width to the RAV4 sport utility and up to 3 inches to the 4Runner, Sienna, Tacoma and Avalon. The goal was both comfort and extra interior space to help protect passengers in side-impact crashes, according to Toyota’s Paul Williamsen.

For its part, Ford Motor recently started using what it believes are the industry’s first set of virtual mannequins depicting nine different body types – including a hulking man – in computer-aided design. Reason: a finding that the average near-biggest man grew 27 pounds heavier and nearly an inch-and-a-half wider in the hips from 1962 to 2000.

"For the first time, we’ve made these virtual dummies to reflect people’s growing sizes," Ford spokeswoman Jennifer Flake says.

Ford is also paying attention to comfort of the seats themselves. The automaker is researching whether to install power massage units in the backs and cushions of its seats.

It’s also considering inflatable bladders in the seats to make them fit passengers of different sizes.

"When you think about how much time people sit in a seat – the average time commuting has gone up dramatically – it’s staggering," says Susan Dehne, the automaker’s chief engineer of seat systems.

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