How Center-mounted Airbags Work

It may look a little strange, but a center-mounted airbag might keep you from smacking skulls with the other front seat passenger during a side-impact collision or rollover. Want to learn more? Check out these car safety pictures.
Courtesy of General Motors

Let's get this out of the way right up front: It's probably not what you think. A giant airbag does not shoot out of the dashboard and expand all the way across the cabin to pillow both front occupants like one of those big body pillows. A center-mounted airbag is one squiggly little kidney-bean-shaped thing that pops out of the driver's seat.

As of 2013, only three cars in the world will be equipped with these airbags: the Buick Enclave, GMC Acadia, and Chevrolet Traverse (all crossover-sized vehicles). It turned out that automotive industry supplier Takata was independently researching side-impact safety at the same time as General Motors. Rather than struggle alone, teams headed by Scott Thomas at GM and Richard Wiik at Takata joined forces. The center-mounted airbag that was born of this collaboration was 5 years in the making and resulted in nearly a half dozen patents.

Lest you picture a vehicle cabin filled with suffocating airbags, you should know that this airbag only comes out when it's needed and it doesn't stick around forever. And like every other safety system in your car, when it comes to an actual crash, your seatbelt is still number one for staying safe. Airbags can only help you if your body is not flying around the car.

So what good is this highly specialized airbag? Why spend so much time and energy on a weird-looking airbag that pops up between the seats? Three words: head-bonk prevention.

Stuck in the Middle with You

Some dummies get together to demonstrate center-mounted airbag effectiveness.
Some dummies get together to demonstrate center-mounted airbag effectiveness.
Courtesy of General Motors

In the quest for head-bonk prevention, GM and Takata came up with a clever solution. Say you're cruising along and some dimwit runs a red light and T-bones your car. Or you hit a patch of black ice and slide into a telephone pole. Or your car gets kicked in the door by an AT-AT because you are driving on the planet Hoth in "The Empire Strikes Back." Any of these scenarios would be picked up by the sensors placed all over your car.

The sensors would trigger the airbag to deploy from the side of the driver's seat, right over the frozen Slushee you've got in the cup holder. The designers at GM and Takata were clever enough to make the airbag pop out in a curved shape so it doesn't literally blow up in your face. The odd-shaped airbag is designed to hold onto the driver and keep him or her from flying across the cabin to the other side of the vehicle. "We're trying to hook 'em," said Thomas, the lead engineer on this project at GM.

There a membrane that keeps the airbag upright between the two seats, so it works even if the driver is the only person in the car. But, since an airbag conveniently has two sides, the one center-mounted bag prevents a serious head-bonk situation between the driver and passenger. Still images from the crash test dummy sessions make it look like the dummies are snuggling and sharing a pillow while they nap; but in reality, they're avoiding the dreaded head bonk. Dummies.

The center-mounted airbag will only deploy when you're being kicked by an AT-AT in the side of the vehicle -- or in a rollover. But if you simply bang bumpers in traffic, or the AT-AT comes at you from behind, it will not deploy. As Thomas pointed out, you don't want it to deploy until you need it. Say the AT-AT kicks your rear bumper -- that might deploy your front airbag. But if he kicks hard (and you know he will), it could send your car rolling over a cliff. That's when you'll want the center-mounted airbag, and that's when you'll get it. "It's always there when you need it later," Thomas said, which sounds very comforting. Even on Hoth.

Is Head Bonking Prevention Important?

How dare you even ask such a thing! Of course head bonking prevention is important, and it happens a lot in side-impact collisions. And there are some terrifying numbers to back it up -- and keep you awake far into the night:

  • Nearly 40 percent of front passenger fatalities in non-rollover crashes are caused by side impacts
  • The head and torso are the most frequently injured body parts in side-impact collisions
  • Engineers call the torso the "thorax," which makes humans sound like insects, which is 48 percent unacceptable
  • When the driver's head is bonked, it's most often against the passenger's head (29 percent of the time), but also against the passenger's body (21.7 percent), and even as far as the passenger door (15 percent)
  • If there is no passenger against which to bonk one's head, the driver will smoosh his torso against the center console 39 percent of the time
  • In each of these scenarios, 100 percent of the occupants were wearing seatbelts, but there was no center-mounted airbag installed in the car

[Source: General Motors]

The statistics can be broken down even further, depending on if the occupant is on the "near side" or "far side" of the crash. The center-mounted airbag is designed to do the most good in a far-side impact, when the crash occurs on the opposite side of the vehicle from the occupant. That's when you're most likely to get tossed sideways like a sailor in a storm.

During testing, GM even went so far as to thrust a big metal pole into a test car as far as the center line of the empty passenger seat. The dummy in the driver's seat tipped all the way over and bonked his head on the pole. You would have to do some radically terrible driving (or be kicked in the passenger door by an AT-AT), to end up in that kind of crash in real life, but if you did, it would probably define the term "bad day."

The good news: A center-mounted airbag can prevent a lot of this type of head-bonking in side-impact crashes.

Where Can I Get This Head Bonking Prevention Technology?

Scott Thomas, a senior staff engineer for General Motors, demonstrates how a center-mounted airbag works.
Scott Thomas, a senior staff engineer for General Motors, demonstrates how a center-mounted airbag works.
Courtesy of General Motors

As was pointed out at the beginning of this article, the center-mounted airbag was brand-new on only three vehicles in 2013, and GM wasn't ready to say yet which other models might be next to get it.

If it prevents head-bonking so well, why not just throw it into every car in the fleet, you ask? Good question! The answer is simple: It doesn't fit. Airbag packaging, with the bag itself and the little explosives that set it off and the electronics that tell it when to go, is pretty bulky. Yet, in regard to some of GM's crossover-sized vehicles, like the Enclave, Acadia and Traverse, Sharon Basel at GM said, "the size of seat allowed us to get it to market much quicker." Putting a big bag like this, packed with explosives, into a tiny commuter car would have been an engineering nightmare.

The other reason, Basel pointed out, was that crossovers are really popular family vehicles. They're more likely than some teensy commuter car to have occupants in both the passenger and driver seats. As much as everyone wants to keep you from squishing your spleen against the center console, we really want to prevent the driver and passenger from knocking each other out (or worse) with a solid head bonk after a side impact.

Since this technology is so new and in so few cars, it's neither regulated nor required by the U.S. federal government. Basel made it perfectly clear: "This is an industry first in terms of concept, development, design, engineering and getting it into the marketplace."

You may still be wondering -- even after all of this information -- if a glorified balloon in a weird shape will actually stop a "supersized" American from pitching into the passenger seat. It will indeed. Thomas, along with Richard Wiik at Takata, designed the airbag to "give appropriate coverage and restraint for larger occupants." As high school physics teaches us, a larger body will have more energy. And if the center-mounted airbag works for the big guys, it'll work for anybody.

Author's Note: How Center-mounted Airbags Work

Sometimes, if you're lucky, you get to prove what an ignoramus you are -- even in your chosen field of expertise. This was one of those times.

I assumed that a center-mounted airbag would be in the center of the dashboard. Like, where the LCD screen is. When I emailed the kind folks at GM about an interview for this article, I tried to sound all smart, and as if I'd done tons of prep work. In truth, I'd only heard of center-mounted airbags about twenty minutes before. So I was all, "What might the drawbacks of such an airbag be? Does it displace the LCD screen or cause a major redesign of the air vents?"

The GM guy was all, "Um, no. It doesn't come out of the dashboard. It's mounted in the seat."

Which, once I'd actually looked at the press release I held in my hand and the pictures that came with it, was painfully obvious. The upshot was that when I finally did get an interview with the guy who kind of invented this thing, I didn't pretend to know any more than I did, and I made sure to review all the materials I had before talking to him. Lesson learned.

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  • Basel, Sharon. Manager of Environment and Energy Communications for General Motors. Telephone interview conducted on Jan. 10, 2013.
  • General Motors press release. "GM Introduces Two Industry-First Safety Features." Sept. 30, 2011. (Jan. 16, 2013)
  • Thomas, Scott. Senior Staff Engineer for General Motors. Telephone interview conducted on Jan. 10, 2013.