Creating the Perfect Fit: New Car Seat Design

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

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.

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."

Customizing Vehicle Seat Comfort and Convenience

Customizing Vehicle Seat Comfort and Convenience

A few years ago, Toyota engineers decided to play corporate nanny and deliberately designed a vehicle seat they figured consumers wouldn't like. Americans needed to demonstrate better posture, they believed, and if only drivers would sit erect in it, this seat would eliminate back fatigue. But if drivers slouched, their muscles would tire and ache.

Not a good idea. "It got just terrible reviews from the market, because the customer didn't appreciate being 'told' exactly how they needed to sit," admitted Michael Sweers, who at the time was one of those patronizing engineers — and now is general manager of engineering design for Toyota Motor Engineering & Manufacturing North America. Toyota won't reveal which vehicle that seat was in but, Sweers said, "We learned."

"In days gone by, it was just a seat," said Roger Campbell, a seat-engineering supervisor for Chrysler. "But now, with competitive pressures in the marketplace and technology advancing, we're really migrating toward being able to take customer data and their wants and create systems that delight the customer."

Nowadays, car seat designers are harnessing digital technology to get more precise and objective ideas of what kind of fit will please the most commonly shaped consumer and yet also extend to the needs of the smallest and largest Americans. Vehicle seat supplier Lear, for example, has a patented process it calls Comfortech that involves "pressure mapping" of hundreds of individuals while they're sitting in car seats, to determine ergonomic "hot spots" where designers must make comfort adjustments.

Fitting Body Parts in Seat Parts

Each aspect of the human body poses distinct design and engineering challenges for the car-seat part to which it corresponds.

Backs: Seat designers pay more attention to backs than anything else because how our backs fare is the biggest overall determinant of whether a seat feels comfortable. But it is getting more difficult to satisfy everyone, in part because Americans' posture varies. GM, for example, has identified at least three broad posture categories — erect, normal and slouching — each of which presents different design challenges.

Cushions: The biggest challenge in designing cushions is combining initial plushness with the underlying firmness required to prevent muscle and joint fatigue. Designers often handle that by putting a thin pad of soft foam underneath the cushion-trim material, then layering that over a denser base consisting of hard foam, springs or a combination.

Thigh support is the peskiest aspect of cushions. "If your thighs don't have enough contact with the cushion, you create a pressure point where you're actually sitting on your tailbone, and your weight isn't distributed," explained Sweers of Toyota. "An hour or two along, you get 'tailburn' — a lower backache. Most people associate that with not having enough lumbar support, but it's really the pressure on your tailbone."

So seat designers can make cushions longer or wider, or make them electrically movable. But they also have to watch out that the calves of shorter drivers don't come into contact with the longer cushions. That's where adjustable pedals come in especially handy.

Bolsters: More American consumers want bigger and more stylish bolsters, as in many high-end and performance vehicles. But bolsters that are substantial enough to make you feel snug in your seat also pose some very practical problems. For one thing, having to slide over them makes it more difficult to get into and out of a car seat. Plumper bolsters also limit the amount of "leg splay," or room for your legs to move — a certain amount of which you need to be able to operate the pedals freely.

And because people are wider, more aggressive bolsters are making seats uncomfortable for individuals beyond certain widths. "The trick with bolsters is to have different zones of stiffness" within the bolster that get firmer with distance from the legs, said Terry O'Bannon, a principal engineer for Lear. Using foam with various thicknesses, densities and compression properties, "you can almost separate the look of the seat from how the bolsters are going to feel."

Designing the Seats

Designers take these disparate concerns and integrate them into comfort targets for a seat system. The main tools of their trade include the polypropylene and polyethylene foams that they layer horizontally or vertically, at various densities and flexibility levels, to form unique seat contours.

Adjustment hardware is another key part of designers' arsenals. Most midmarket and upper-segment vehicles offer electric controls that move seats front and back, and up and down. High-end models also provide separate electric adjustment of back and cushion angles, as well as lumbar supports and even electrically adjustable bolsters.Carmakers also are paying more attention to factors other than seat construction and adjustability that contribute to comfort or discomfort. Heated seats, for instance, now are available in just about all high-end and midmarket vehicles. An increasing number of vehicles are offering seats that cool as well.

Some cars, such as the 2007 Cadillac DTS, have even harnessed the technology for explicitly therapeutic purposes by offering heated seatbacks only. "It's like taking your heating pad with you," said Mark Grajek, GM's lead engineer for human vehicle integration. At the same time, GM recently discontinued a previous DTS option of a massaging driver seat. "It was hokey" and didn't work well, Grajek admitted.

It's a Different Ballgame Past the First Row

Car seat designers are turning more attention to second- and third-row seats, in part because of the increasing versatility that many vehicles require in their space behind the first row. "The front row is where the owners sit, so we used to mainly be concerned about that," said GM's Grajek. "But the challenge now is to allow people in the other rows of seats to get comfortable and have good posture, too."

In second and third rows, body types and sizes vary even more than in the front row, because kids often sit in the back. Rear seats routinely must fold, split, stow away and be removable — yet also provide comfort over the course of a long ride. Another recent wrinkle is the need to design around the battery packs of hybrid vehicles, which typically reside under rear seats.

While innovations such as Chrysler's Stow 'n Go seats in minivans have made rear seats more flexible, there's now more emphasis on comfort. The 2008 Chrysler minivans, for example, offer swivel seats in the second row that make entry and exit easier. And the second row of seats in the new Toyota Tundra truck offer cushions that slide forward to give passengers more of a reclining position, even though the seatbacks are fixed.

Seats as a Brand Differentiator

Seat engineers also are working more closely than ever with vehicles' chief designers and stewards of brand equity to better match comfort characteristics with each model's personality and the preferences of target demographics.

As GM's Grajek explained it, "We're making sure the character of the seat matches the customer. So that could mean, in our high-performance vehicles, going after a high-bolstered, BMW-type seat, to producing more of a Lexus-type seat for an older crowd."

And Nissan's seat contours tend to be aggressive, just like its design-first brand mentality. "You get direction from the ergonomics standpoint, and then from your actual brand-identity statement. You have to add in what the personality of the seat is going to be so it meets the personality of the vehicle," said Lawrence Smythe, a senior project engineer for Nissan. "You balance those two things to create an experience that is consistent with the entire vehicle experience."

Because seat comfort is ultimately such a personal preference, it's difficult even for Edmunds.com to come up with an overall list of the "most comfortable" vehicle seats on the road today. Generally speaking, the high-end brands like Lexus and Mercedes-Benz offer highly adjustable driver seats, and that alone increases the likelihood of finding a comfortable position. Many Edmunds editors feel that Honda and Volvo seats are generally comfortable, but exceptions exist there as well. (Some taller staffers have been unhappy with the seats in the Honda Fit, for example.)

In the end, every car shopper would benefit by keeping seat comfort top of mind during a model's test-drive.

Oh, My Aching Back! Lumbar Support and Head Restraints

Oh, My Aching Back! Lumbar Support and Head Restraints

Because your back plays such an important part in how you feel no matter where you are, making a seat comfortable in terms of back support remains the highest aim of vehicle seat designers.

But it's getting more difficult for car seat designers to ease everyone's back in the cockpit. Larger bodies are more difficult to fit properly. And as we age, our spines curve more, meaning that auto companies have to pay special attention these days to the aging baby boomer demographic.

"There are seven different theories about what causes lower back pain," said Terry O'Bannon, a principal designer for seat supplier Lear. "But the main thing we focus on in seat design is reducing postural muscle activation. If you're having to hold yourself up when you sit down, then the muscles are continually having to work. And you get fatigue and joint pain."

Paying Attention to Lumbar Support

Lumbar support is crucial to this effort. Overall, the auto industry is acknowledging its importance by generally, and gradually, increasing the frequency of lumbar-support systems in seats and their provision as standard equipment, Edmunds.com research shows.

For 2007 model-year vehicles, 78 percent offer driver or driver/passenger lumbar support as standard or optional, a significant rise from 71 percent of models that did so for the 2004 model year, according to Edmunds.com research.

This model year, 29 percent of models offer driver-only lumbar support on a standard basis, the research found, up from a comparable figure of 26 percent for the 2004 model year. Meanwhile, 45 percent of models for the 2007 model year offer driver/passenger lumbar support as standard or optional, up from 43 percent in 2004.

Yet the consensus of the seat-design community is that, in general, import brands are making lumbar supports more widespread, or more often standard, while the domestic Big Three are more likely to be "decontenting" the vehicle of lumbar supports in cost-cutting moves.

"We see our Asian customers generally increasing the use," said Barry Jones, president of Leggett & Platt Automotive Group North America, a Windsor, Ontario-based operation that relies on lumbar supports for more than half of its revenues. "And we see our North American customers maintaining where they're at or slightly decreasing."

Sometimes, carmakers chip away at costs by removing lumbar supports from the front passenger seat while leaving them on the driver side. "From driver to passenger side, it's a constant battle on the front row," said Mike Grajek, General Motors' lead engineer for human vehicle integration. For the sake of costs and profit margins, automakers neither want to "give away" lumbar supports compared with competitors, nor make them glaringly absent.

Overall, car seat designers acknowledge the growing importance of lumbar support to consumers. "When you have lumbar support and the following [model] year that support is taken out for some reason, the seat sees a dramatic decrease in comfort," said Don Bernhardt, Lear's vice president of seat engineering. And consumers know it right away."

How Lumbar Supports Work

Usually, lumbar-support systems in seats are built mechanically around a metal plate that has a surface of as much as a square foot, sometimes resembles a rib cage and weighs a pound or two. Other systems are pneumatic, meaning a bag is inflated. Typically, lumbar supports can be manually or electronically activated to extend into the seat cover and gently push the support into the lumbar areas of the lower back.

A number of variables can determine how effective a lumbar-support system is in practice, including the materials used, how well the system is integrated with the rest of the seat and whether adjustments move only in and out or also up and down.

"Consumers want the flexibility of adjustable lumbars," said Steve Nunez, supervisor of seat-comfort attribute development for Ford. "There are so many different sizes and shapes of customers that we can't find the single optimal spot for lumbar support. And people are aging and have different back ailments and conditions. Adjustable lumbars allow us to find the sweet spot to offer them the most relief and give them the best posture."

Head Restraint Rule Complicating Seatbacks

The latest challenge facing seat designers is a new federal whiplash-prevention standard; it requires both front and rear headrests to be higher and closer to the backs of people's heads, similar to those mandated by the European Union. So beginning in September 2009, U.S. automakers will have to phase in head restraints that lock once they're in position and aren't removable — including those on rear seats that tilt or fold for loading purposes. Vehicle seat designers must choose between placing "passive" restraints closer to occupants' heads or designing "active" mechanisms that instantaneously move restraints forward to support the head if a vehicle crashes. (For details, see "Pain In the Neck.")

But consumers have demonstrated that they will tend to resist, by whatever means necessary, having restraints moved closer to their heads. "The occupant gets a pressure feeling," said Michael Sweers, general manager of engineering design for Toyota Motor Engineering & Manufacturing North America. "It doesn't affect their comfort, but it's like being in a tight space and you feel like it's touching you."

Many consumers, research predicts, will simply recline their seatbacks more. This maneuver, of course, tends to offset the back and lumbar support that has been built into these seats and makes it more difficult for designers to make the seats comfortable and supportive of the back. Automakers and seat suppliers are responding in part by adding more foam in upper seatbacks so they are more upright and the neck-to-torso angle is more comfortable, said Ford's Nunez.

Still, certain types of drivers probably are predicted to resist the most. Boomers are less accepting of the closer head restraints than younger drivers, the companies say. Women, out of concern for their hairstyles, are more disconcerted by closer restraints than men are. The shortest drivers will have the biggest problems because they must keep the seat high and the backrest extremely vertical.

And in the American West, automakers expect complaints from drivers who prefer wearing cowboy hats to putting up with a head restraint: Now, they'll have to take off their 10-gallons before they sit down.

Add the new head-restraint standard to the list of reasons why designing seatbacks — and cushions, and bolsters — is still as much an art as a science. And it will be as long as drivers are, well, human.

Dale Buss is a journalist and author based near Detroit.