Bigger Bags, Better Glass

Forty years after automakers fought off regulations that would have actually tested rollover occupant protection, the National Highway Traffic Safety Administration has published a final ejection mitigation rule, which favors the installation of bigger and more longer-deploying  side airbags and takes a half-step forward on improving side glazing.

The rule establishes a new Federal Motor Vehicle Safety Standard 226 Ejection Mitigation. FMVSS 226 applies to the side windows next to the first three rows of seats in motor vehicles with a gross vehicle weight rating of 10,000 pounds or less. The performance-based standard would institute a compliance test in which an impactor would be propelled from inside a test vehicle toward the windows. The ejection mitigation system would have to prevent the impactor – based on the mass imposed by a 50th percentile male’s upper torso on the window opening – from moving more than a specified distance beyond the plane of the window.  Each side window would be impacted at up to four locations around its perimeter at two time intervals following deployment, to ensure that the airbags remain deployed for the beginning and end stages of a rollover.

The ejection mitigation rulemaking was mandated under the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users, the massive transportation bill of 2005. NHTSA was to have issued a final ejection mitigation rule by September 1, 2009, when SAFETEA-LU’s funding expired.

The proposed rulemaking, published in December 2009, made a stronger push for laminated side glass as a partner with side airbags in keeping occupants contained:

“Advanced glazing could have a role in complementing ejection mitigation curtain systems. NHTSA tested several vehicles’ ejection mitigation side curtain air bags both with and without laminated glazing to the 18 kg impactor performance test proposed in this NPRM. In the tests, the glazing was pre-broken to simulate the likely condition of the glazing in a rollover. Tests of vehicles with advanced glazing resulted in an average 51 mm reduction in impactor displacement across target locations. That is, optimum (least) displacement of the headform resulted from use of both an ejection mitigation window curtain and advanced glazing. To encourage manufacturers to enhance ejection mitigation curtains with advanced glazing, this NPRM proposes to allow windows of advanced laminated glazing to be in position, but pre-broken to reproduce the state of glazing in an actual rollover crash. Although the glazing is pre-broken, the laminate in combination with the remaining integrity of the glazing acts as a barrier to ejection.”

To encourage manufacturers to enhance ejection mitigation curtains with advanced glazing, the NPRM proposed to allow advanced laminated glazing to be in position, but pre-broken to reproduce the state of glazing in an actual rollover crash.

But the agency made it clear that it was not married to this aspect of the proposal. It debated the merits of testing with movable laminated glass windows up or down or pre-broken, and put the question out to automakers. But, the agency also noted that it was loathe to completely disembowel the incentives for laminated glass:

“The agency is contemplating alternatives to the approach of allowing windows to be in place and pre-broken. One option would be to test with all movable windows removed or rolled down, regardless of whether the window is laminated. Fixed laminated windows would continue to be kept in place, but pre-broken. This would assure that the ejection mitigation performance of vehicles with laminated windows is equal to those without laminated windows, when the windows happen to be rolled down. However, this would not provide an incentive to vehicle manufacturers to install advanced glazing in movable windows.”


In response to the NPRM, Automakers – notably Honda and Ford – argued that in real-world rollovers, advanced glazing is often detached from the frame and pre-breaking it for a test configuration didn’t simulate what happens in a rollover. This prompted the agency to take a split-the-baby-in-half approach.

Under the new standard, movable advanced glazing can not be the sole means of meeting the displacement limit, and the 16 km/h-6 second test must be performed without it. The agency argued

“This approach will assure a reasonable level of safety when side glazing is rolled down or when the severity of the rollover damages or destroys the effectiveness of the glazing, and still encourages the use of advanced glazing as a countermeasure to supplement the vehicle’s performance in meeting the 20 km/h-1.5 second test.”

So, will this really encourage the installation of laminated side glass? Or does it delay it?

Part Ardis, a Memphis attorney who has litigated ejection cases and a long-time advocate for laminated glazing, has argued that laminated glass should be used in conjunction with side airbags to complete the occupant protection system.

“Seat belts restrain, they do not retain,” he says.

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