Door locks on the center stack. Heated-seat controls near the floor. And the auxiliary jack? Nowhere in sight.

Welcome to today’s vehicle interiors, where the proliferation of features demand corresponding growth in the number of dials, knobs and buttons – all of which compete for the same space.

It can take as long as a sitcom to find controls that are never quite where you’d expect.

And once they’re found, they don’t always function as anticipated.

“It used to be you just pushed a button and you got a radio preset,” says Thomas Mutchler, senior automotive engineer for Consumer Reports magazine. But with today’s infotainment-type systems, “I toggle over to presets, nudge up, push down, turn the dial, the screen comes on.”

Ironically, one person’s problem is often an OEM’s carefully researched solution.

With the ’10 Chevrolet Equinox, Creative Design Lead Chris Hilts says General Motors Co. went “European” by placing the door-lock/unlock switches on the vehicle’s center stack. The migration was based on finding an easy-to-reach spot for a small-statured woman.

“Most of your controls are dictated by architecture and reach curves,” Hilts says. “When you start putting the vehicle together, you set up the occupant position, and then you have a set of reach curves. And your controls are laid out against those reach curves.”

Because the Equinox is geared toward families, Chevy skewed its interior design in favor of women. “We took careful consideration to accommodate for the 5th percentile female,” Hilts says.

But the deal was sealed when feedback from previous-generation Equinox owners reported the vehicle’s door locks really pushed their buttons. Located on the door panel, they were subject to inadvertent locking – a claim that bewildered Chevy designers and engineers until the phenomenon occurred within their ranks.

“Everybody here at the design center has locked themselves out of one or two of our products at one point,” Hilts says. “Once you do it, you understand placement of controls is very important.”

But because doors and door-locking mechanisms are linked in the consumer’s psyche, Mutchler says a preferable solution would be finding a better location on the door panel. Doing otherwise simply kowtows to cost.

“You’re not running wires through the doors,” he says of the new Equinox. “And it’s one switch instead of two.”

Mutchler says door-lock switches on the center stack, also found on the all-new ’11 Ford Fiesta, “just get lost” in an expanding maze of controls.

Similarly, many auto makers are struggling with locations for a USB port and/or iPod jack, says Fred Lupton, manager-Human Factors & Lighting Group at Toyota Technical Center in Ann Arbor.

“Do you put it inside a storage bin, where you can tuck it away and then forget it, (and) then every time you get in and out of your vehicle you’re opening up and closing your center console?” he asks. “Or do you leave it out where you can plug in easily and then drop your MP3 player into your cupholder?”

For security, Mutchler says Consumer Reports advocates for a USB port/auxiliary jack to be hidden, as in the ’11 Jeep Grand Cherokee. The SUV’s iPod connector is located at the base of the center stack in a covered bin akin to a modern kitchen’s appliance garage.

But the USB port in the new Fiesta is “right in the middle of the console, right underneath the hand-brake lever (and) totally open. So when you stop, you have to take out your iPod; you have to take out whatever you have plugged in there so it doesn’t get stolen.”

Meanwhile, David Graff, automotive industry director at Microsoft Inc., suggests an end to the dilemma is on the horizon.

“You’re going to see a lot more wireless (connectivity),” Graff says. “But that’s going to be a little while.”

Lupton says heated- and cooled-seat switches pose another headache for engineers and designers. Today, such controls are placed anywhere and everywhere: on the center stack, center console or, in the case of the ’10 Toyota Prius midsize sedan and Honda Odyssey minivan, near the floor.

“We just want to be able to find the button!” Mutchler says, calling the Prius the “worst offender,” with switches below a “giant arch of a console. It really seems like an afterthought.”

Of the Lexus IS and GS, Lupton says the seat switches were located under a sliding armest.

“They were nicely hidden,” he says. “But then it was a 2-step process to get to them. If you’re just looking around for them visually, you wouldn’t find them. A lot of people hated that.”

Mutchler says the next-generation Honda Odyssey is taking a step in the right direction by moving the seat buttons near the heating, ventilation and air-conditioning controls on the center stack.

Oftentimes, controls can be easy to locate, but functionally not intuitive. The issue arose earlier this year for Toyota Motor Corp., when owners alleged their unintended acceleration and reported difficulty shutting down models equipped with push-button start.

Unbeknown to many, Toyota requires a 3-second button compression to shut down a vehicle, which is too long in panic situations, Mutchler says.

“That’s something I can’t explain,” Toyota’s Lupton says. “That was done many years ago in Japan. The obvious answer is you want to avoid inadvertent actuation, someone playing around with the button, accidentally bumping it while driving. I’m sure TMC was being very conservative in trying to protect that switch.”

The Society of Automotive Engineers is working on a recommendation for vehicle shutdown via push-button. Participation among auto makers has risen this year since Toyota’s woes became fodder for media cannons and government attention.

Lupton says early consensus points toward two shutdown methods: a compression of less than three seconds, or a few quick hits.

Larry Smythe, human-machine interface engineer at Nissan Technical Center North America in Farmington Hills, MI, and a member of the SAE group, won’t discuss time increments for each scheme but says the “overriding spirit” of the group’s findings is to “provide the opportunity for manufacturers to solve the problem in their own way,” in keeping with brand image.

But it must be an obvious solution, Smythe says.

All experts agree there is room for improvement when it comes to placement and functionality of switches.

Some see fewer buttons and more functions in a menu-type system, such as Audi AG’s MMI. Others, including Mutchler, advocate for more hard buttons for reduced driver distraction.

“What is the cockpit of the future going to be?” asks Visteon Corp.’s Michael Tschirhart, manager-HMI. “We want it to be more seamless. We want it to be for the driver to have a lot more ease of use and seamless fluency.

“So the things they’re doing really enhance the driving task, making it simpler and more enjoyable and more intuitive.”

Lupton agrees. “Styling is always pushing the envelope as to where controls and displays are going to go to create an image for a vehicle,” he says.

“From a human-factor standpoint, we want to make things very straight-forward, very simple, to keep people’s attention on the task of driving. That’s the fundamental thing people have to do: keep their eyes on the road and their attention on driving.”

– with Eric Mayne

cschweinsberg@wardsauto.com