Tech Talk: Engineers studied kids to help avoid the puke zone
The Toronto Star for Wheels.ca
Little did I realize when I took my first ride in the back seat of a 1998 Oldsmobile Silhouette minivan what an impact the new video-screen technology it introduced would have on the auto industry, not to mention on a whole generation of parents and kids.
What I did realize was that, for the first and only time in my life, I came precariously close to experiencing motion sickness. And that the relationship was not coincidental.
To emphasize the significance of the in-car video system, Oldsmobile named the model the Premiere, and established a co-promotion deal with one of the big Hollywood studios.
At the time, the concept seemed like just another gimmick — a DVD player buried in the back of the centre console with a smallish screen, by today’s standards, which flipped down from the roof between the front-seat headrests.
But who would want to watch movies while riding in a car? A whole generation of kids raised on TV and soon to become the video-game generation, that’s who. And with the full support of their parents, who happily endorsed the new back-seat babysitter.
Oldsmobile quickly lost its exclusivity on the concept, which was adopted not just by other minivans but in station wagons and SUVs as well, and even some sedans and pickups.
Today, the rear-seat video system has become ubiquitous, in many cases with individual screens for each occupant.
But there proved more to the design and engineering of the systems than just sticking a screen in front of a passenger. As it turned out, my borderline brush with motion sickness was not an isolated occurrence.
“We know through other scientific research that, even if our eyes are focused on a fixed point, if we can see the outside passing by in the window, our brain is telling us that we are moving,” explains Don Shreves, head of General Motors human factors engineering group.
“But if our eyes are at a downward angle (such as when reading a book) and do not see the view outside the vehicle, our bodies become sensitive to motion and increase the chance of sickness.”
In the case of my Silhouette experience, I was seeing motion on the video screen, perfectly framed by contrasting motion through the windshield behind it, all supported by the sense of actual motion that results from inside the inner ear. And they didn’t correspond.
According to the U.S. Centers for Disease Control, when your brain gets signals that don’t match, you can get motion sickness.
All of which makes the placement of a video screen a critically important decision.
Given the millions of in-car systems that have now been produced and watched ad-infinitum — hundreds of hours by my own grandkids, alone — it’s safe to say my initial experience was not the norm.
Which suggests either that today’s kids have evolved more tolerance for visually-conflicting images or that the engineering of the systems has improved — or maybe a bit of both.
For its part, GM has learned to place its video screens outside what it calls “the puke zone,” according to Shreves — the screen position most likely to induce nausea when the vehicle is moving.
To help determine just where that zone is, the engineering group enlisted the help of employees’ children during Take Your Child to Work days.
Researchers queried 75 kids to determine when the screen distance was too close or too far away. Their responses were compiled and graphed, then turned over to the engineering team to be integrated into the vehicle’s design, with the goal being to keep passenger’s eyes up and on a given spot.
Presumably, they and other manufacturers have found the sweet spot, since there doesn’t seem to be an epidemic of car-sick kids.
Which is not to say there are none. Many people, both kids and adults, are susceptible to motion sickness, although children seem to be among the most vulnerable.
Although watching in-car videos can be a contributing factor, it’s far from the only one. Anything that causes a conflict between the various motion signals sent to the brain from the eyes can be a trigger.
For that reason, the work of suspension design engineers is also critical in minimizing the potential for motion sickness — but that’s a subject for another column.