Seatbelts can save your life, but they can also potentially cause harm, especially to children or elderly passengers. It’s a problem Ford is addressing with its new inflatable rear seatbelt, which will be the world’s first when it’s introduced on the 2011 Ford Explorer.
The belt looks similar to a regular seatbelt, except that it feels padded. In a crash, it expands to apply the belt’s force over five times as much area as a regular belt, helping prevent injuries such as broken ribs.
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“The idea of inflatable seatbelts has been around for over 50 years, but nobody’s been able to do it before,” says Dr. Steve Rouhana, Ford’s senior technical leader for safety. “We tell people to put kids in the back seat, and we wanted to put this in the rear seats for enhanced protection.”
The belts’ inflation is triggered by the sensor that deploys the front-seat bags, but they don’t work quite the same way. Frontal airbags explode with considerable force, using a hot gas. The seatbelts use canisters that send cold gas flowing through the centre of the buckle to inflate the airbag that’s sewn inside the belt.
While they still expand within milliseconds, the seatbelts don’t inflate as quickly as the front bags, as too much sudden pressure could prove harmful to the occupant. The company tested the belt with dozens of child seats to ensure that it is safe for properly-restrained children.
“As the head moves forward in a crash, it tends to go along in an arc,” Rouhana says. “When the chin interacts with the inflated portion of the shoulder belt, it starts to slow down. That reduces forces on the neck, and we believe it lowers the possibility of neck injury.”
Rouhana’s own son unwittingly led to an important safety enhancement. “Early in the project, around 2002, my youngest son was around six,” he says.
“We were coming home and I looked in the rearview mirror. He was in a booster seat and the belt was wedged between his neck and shoulder. I saw that and thought, what happens if my inflatable belt goes off with him in that position?
“Young children can get their heads on their shoulders, they’re so flexible, and you can’t get a (crash test) dummy’s neck in that position. So we developed a hinge for the neck of the dummy. Nobody did that before, and that takes a lot of time. We were the first in the world, and hopefully we get credit for that.”