Volvo, now a division of Ford, is still obsessed with seats, so much so that it has two separate design groups: 11 engineers who work exclusively on front seats, and nine more for the back. Its seats consistently rank among the industry’s best in safety testing, while offering near-orthopedic support and Scandinavian style to boot. Company engineers note the challenge of creating seating positions that pamper and protect occupants who range from less than five feet to well over six feet tall. One backseat solution hits the market in October: Volvo’s new XC70 Cross Country features built-in child booster seats that rise to two different positions to accommodate children of various sizes.

Today’s smarter interiors and seats may be especially critical for a struggling Detroit. Many domestic designers freely acknowledge that they’ve been working to repair the damage caused by their reputation for poorly crafted interiors, including seats that often lacked the aesthetics and support typical of European brands.

Over the past two years, General Motors has shown the most Motown mojo. Cadillac seats, for example, offer top-grade, semi-aniline leather, with hand-applied stitched-leather and synthetics on doors and dashboards—supplied by the U.S. division of Germany’s Draexlmaier, which has crafted interiors for the likes of Bugatti and Mercedes’s Maybach.

Ed Welburn, General Motors’s chief designer, emphasizes the importance of seats to the car’s interior design. “It all begins with the structure, the support, the right profile to the seat,” says Welburn, only the sixth design chief in G.M.’s nearly century-long history. “We love heated seats and all those toys, but if the basics aren’t there, it’s not going to be comfortable over long distances.”

A trio of G.M. crossover S.U.V.’s—the G.M.C. Acadia, Saturn Outlook, and Buick Enclave—combine stylish cabins with a rarity: a third-row seat that actually accommodates six-foot-plus adults. “Everyone wants more and more interior space, and to give it to them without giving up comfort is a challenge,” Welburn says.

Making seats greener—we’re talking the environment, not upholstery color—is another fertile area for research. Seats in the 2008 Ford Escape and Escape Hybrid S.U.V.’s are wrapped in 100 percent recycled polyester fabric obtained from soda bottle resin; the 2008 Ford Mustang will use a soy-based seat foam that saves energy.

There are also design changes that are being mandated by the federal government. Starting in 2007, every car sold in America has included front passenger seats that can detect whether a small child or a heftier adult is occupying the spot. If the passenger is lightweight, dual-stage airbags launch more gently, lessening the chances of airbag injury. For 2009, new regulations will boost headrest standards for all cars.

Mercedes, for its part, sees seat design as a key element in Driver Fitness, its two-decade program to reduce stress and fatigue behind the wheel while promoting alertness, control, and safety. After monitoring drivers in a wide range of driving conditions, the company determined that S-Class test drivers’ average heartbeat—a key stress indicator—dropped by nearly 1 beat per minute compared with the average for drivers of the previous-generation model and by more than 7 beats per minute compared with drivers of S-Class vehicles built from 1979 to 1992.

That may be a historical about-face. Luxury cars were always supposed to make hearts race; now Mercedes wants to slow them down.