The U.S. National Highway Traffic Safety Administration (NHTSA) has proposed a new federal rule that is intended to reduce the risk of being ejected during a rollover accident.  That proposed rule would require car companies to pass testing that evaluates the risk that a person would be ejected out a side window during a rollover crash.  The government expects that most car companies would meet that standard by adding improved side curtain air bags and also potentially by using laminated glazing (layered glass/plastic/glass) similar to what is used in windshields.

Although side curtain air bags are present in many vehicles today, not all of those are triggered during rollover wrecks.  There are several differences between curtain air bags that deploy only in side crashes and curtain air bags that deploy in rollover crashes.  The rollover-triggered air bags obviously require sensors to detect that a rollover is occuring.  Such rollover sensors were available on nearly 100 models by the 2007 model year.

The rollover air bags also have to stay inflated longer: although side impacts may last less than a second, rollovers can last several seconds.  So, rollover air bags need to stay inflated longer.  This is often accomplished by using a colder gas to inflate the air bag, because colder gas does not leak out as quickly.  The rollover air bag fabric is often coated as well, again to make sure the gas does not leak out as quickly.

Additionally, some of today’s side curtain air bags do not extend to the bottom of the windows; this means that some people, particularly small children, can still be ejected even if the curtain air bag is deployed.  NHTSA anticipates that the rollover curtain air bags required to pass the proposed testing would need to extend downward from the roof to cover the entire window.

Finally, in order to keep the bottom of these curtain air bags in position during the entire rollover impact, it is quite possible that the air bag would need to be tethered (or anchored) near the bottom of the window.  Often, this is accomplished through tethers to the bottom of the pillars that support the roof on sides of the vehicle.

NHTSA estimates that the their proposal would add only about $34 per vehicle, compared to the car companies’ current plans.  That is a small price to pay to save someone’s life or to prevent catastrophic injuries that will last a lifetime.