Interpretation ID: 571.226--Pre-breaking glazing--Parker--17-001042

Mr. George Parker

13488 Victory Gallop Way

Gainesville, VA 20155

Dear Mr. Parker:

This responds to your letter concerning the procedures in Federal Motor Vehicle Safety Standard (FMVSS) No. 226, Ejection mitigation, for testing side window glazing. Your first question asks if your understanding of the procedures for pre-breaking advanced laminated glazing is correct. As discussed below, we generally agree with your understanding, but we wish to correct a point. You next ask whether a transom section for ventilation that has no headform target locations is excluded from compliance testing. As discussed below, our answer is yes.

Background

The National Highway Traffic Safety Administration (NHTSA) issued FMVSS No. 226 to reduce complete and partial ejections of vehicle occupants through side daylight openings (windows) in rollover crashes.[1] The standards performance requirements ensure that side windows employ ejection mitigation countermeasures in rollovers. To assess compliance, an 18-kilogram (40-pound) impactor is propelled from inside the tested vehicle toward the tested window at points around the windows perimeter, at two different speeds and time intervals. The ejection mitigation countermeasure must prevent the impactor from moving more than a specified distance beyond the plane of the opening.

Manufacturers typically use side curtain air bag technologies and/or advanced glazing to meet FMVSS No. 226. If advanced glazing is used, different test procedures apply depending on whether the glazing is fixed in place or movable[2] and whether the glazing is used with side curtain air bag technology. FMVSS No. 226 sets forth the test conditions for the impactor test which assesses the expected performance of the ejection countermeasures in an actual rollover crash. FMVSS No. 226 includes a pre-breaking procedure that can cause the disintegration of tempered glazing or damage advanced glazing, thus duplicating the typical condition of glazing in real world rollover crashes.

Question One

You ask about the pre-breaking procedures of the standard (S5.4.1). You refer to the following statement in NHTSAs September 9, 2013 (78 FR 55138) response to petitions for reconsideration of the final rule establishing FMVSS No. 226: There is never a situation under any part of the standard in which glazing is left in place and unbroken. (78 FR at 55161, col. 2.) You ask: Does unbroken only mean the glazing is subject to the pre-breaking procedure regardless of the outcome of applying the procedure as opposed to actually broken, and that the displacement tests are then conducted with the glazing in place?

Answer: We read your question as having several parts to it, so it may be helpful to restate it as follows: Does advanced glazing need to actually break when subjected to the pre-breaking procedure? Assuming it does not, is the advanced glazing (that has been subjected to the pre-breaking procedure) left in place for the impactor test?

The answer to the first part of the restated question is no, under FMVSS No. 226s pre-breaking procedure (see S5.4), the glazing does not need to actually break in the procedure. S5.4.1.2(a) specifies that pressure is applied using a center punch device only once at each mark location, even if the glazing does not break or no hole results. While the procedure does not require the breakage of the glazing as the outcome of the procedure, as a practical matter, tempered glass will shatter and completely evacuate the opening during the procedure.[3] Advanced laminated glazing is not likely to shatter, but typically cracks at the locations of the center punch application. (Hereinafter, we refer to advanced laminated glazing that has undergone the pre-breaking procedure as conditioned glazing.)

As to whether the conditioned glazing is left in place for the impactor tests, the answer depends on whether the glazing is fixed or movable.

The high- and low-speed impactor tests are specified in S5.5(a) and (b) of FMVSS No. 226, respectively. For all applicable impactor tests at both test speeds, under S5.5, fixed conditioned glazing can always be left in place at the manufacturers option (see S5.4). However, for the low-speed test under S5.5(b)--which only applies if the vehicle has an ejection mitigation countermeasure that deploys in a rollover--if the glazing is movable, it is removed or fully retracted prior to testing.

Question Two

You ask for concurrence with your statement that if a side window has a transom section for ventilation for which there is no headform target locations that the transom section is [excluded] from the standard.

We agree with your statement with an assumption. S4.2.1.3 of FMVSS No. 226 states: If a side daylight opening contains no target locations, the impact test of S4.2.1 is not performed on that opening. Side daylight opening is defined in S3 of the standard. If your transom section is a discrete side daylight opening that contains no target locations, the transom section is excluded from impactor testing. If it is not a discrete side daylight opening, the transom section could be part of the side daylight opening to which it is adjacent.

I hope this information is helpful. If you have further questions, please contact Deirdre Fujita of my staff at (202) 366-2992.

Sincerely,

Jonathan C. Morrison

Chief Counsel

Dated: 3/7/18

Ref: FMVSS No. 226