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Creating the Perfect Fit: New Car Seat Design

Trying To Please All of the People, All of the Time

(updated April 30th, 2009)

To imagine the challenge of being an automotive-seat engineer these days, picture one of the hugest men you know — a massive American male in the 95th percentile for weight, at least 267 pounds. Add a 5th-percentile woman, who's not growing nearly as fast as the largest men. And throw in someone with lower-back pain.

Now, design a single seat that will happily cosset each of these physically and physiologically diverse individuals, not just as they settle in and get comfortable — but for the entirety of a four-hour drive.

Now you understand what the automotive industry is up against.

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Car buyers are getting more size-diverse, more ergonomically distressed and more demanding of power adjustments and other amenities, and seat developers are responding. They're using more versatile materials, new engineering techniques, digital technologies and some design flair in attempts to make sitting in a car as comfortable as — or even more — than sitting in your living room.

"The vehicle becomes part of you, and your primary connection to your vehicle is your seat," said Lawrence Smythe, senior project engineer for Nissan. "You make all of your spatial judgments from the seated position. So you're essentially wearing that vehicle. That's why the seat is so important from the ease of driving perspective as well as comfort."

If Only We Weren't So Human

Back in the day, consumers simply darn well sat on whatever the vehicle maker gave them to sit on. Hard benches were de rigueur during the industry's earliest days. Even into the 1980s, rather unadorned bench seating front and rear was a common sight in many cars and trucks. Automotive seat design only became a crucial discipline over the last generation as Americans spent more and more time in their vehicles and as interior comfort and appointments became a major competitive battleground.

Federal regulations dictate seat design only minimally, with the most important requirements concerning head restraints (a.k.a. headrests). And there are distance requirements between the driver's torso and the steering wheel, a space that also can be governed by telescoping steering wheels and adjustable pedals. In the end, automakers mainly must make sure the seat design helps the car pass the government's crash-safety standards.

Comfort and ergonomic functionality have become the focal points of seat design. And in those areas, improvements are being driven by customer demographics, consumer demands and competitive factors.

The No. 1 consideration: Americans are getting bigger and heavier, for the most part. Each company tries to design seats that can accommodate everyone from the smallest females to the largest males, sometimes stretching as far as from the 2.5th-percentile woman to the 97.5th-percentile man.

Both extremes are getting more difficult to address, with the 95th-percentile American man now weighing about 24 pounds more than he did two decades ago. At the same time, while U.S. women in general also have gotten larger, the influx of immigrants from Asia actually kept the overall increase in the size of the 5th-percentile American woman down to under 5 pounds over the last two decades.

Just as airlines and home-furniture manufacturers have had to respond to our wider girths by making seats bigger, auto companies are faced with having to squeeze bigger people into cabins that are getting tighter again with higher gasoline prices. "People want bigger consoles and map pockets in the doors but they also want their seats to be more comfortable," said Steve Nunez, a seat-engineering supervisor for Ford. "So we fight for every millimeter that we can."

At the same time, seats must secure tiny drivers and allow them to see clearly over the steering wheel and reach the accelerator and brake pedals.

And if larger-than-average and smaller-than-average consumers don't feel accommodated when they try things out in the showroom, they go elsewhere. "It ends up being something subtle that still shows up in sales," said Terry O'Bannon, principal engineer in advanced materials and comfort engineering for Lear, a leading automotive seat supplier. "If someone can't fit in a car, they won't buy it."

Aging, Globalization, Competition Come Into Play

The aging of the American population poses its own difficulties, particularly the boomers' move into their sixties. "Younger demographics like seats harder, but as you get into the middle of the baby boomers and older, they're used to having a very soft seat, and they've come to expect that of a vehicle," said Michael Steers, general manager of engineering design for Toyota Motor Engineering & Manufacturing North America. "Whether we think it's truly the best seat for them or not, in an ergonomic sense, isn't as important."

Moreover, more consumers are carrying specific maladies of aging into their cars, including back pain, aching knees and a general decline in the basic nimbleness required to get in and out.

It's one thing to design a single seat that can fit and even ease the joints of the smallest to the largest Americans. But as automakers increasingly globalize vehicle platforms, their seats also have to be able to accommodate the diverse body proportions, size ranges and consumer preferences of people around the world.

For example, while Europeans definitely prefer longer cushions, and Asians like shorter ones, Americans are somewhere in between. And in China, automakers need to make sure that the second row is as comfortable as the first: As many as 40 percent of car owners can afford to hire a driver, and they tend to sit in the right rear seat, said Mark Grajek, lead engineer for human/vehicle integration for General Motors.

At the same time, as Americans spend more time inside their vehicles, every automaker is trying to improve its interior appointments and comfort in noticeable ways. Some of them are even trying to create "seat signatures" that transmit their distinct brand values every bit as effectively as distinctive exterior styling.

"Ford seats have a Ford character now," said Ford's Nunez. "We want you to be able to tell it's a Ford seat by how it feels and holds. We want seats to have a consistency of Ford DNA across the product lineup, whether it's a Fusion or an Escape."

At Nissan, "Our brand image includes the fact that we try to make vehicles that are bold and thoughtful," said Smythe. "So the contours of our seats are bold, but thoughtful so that you're comfortable within them."