Interpretation ID: nht91-7.9

DATE: November 14, 1991

FROM: Edward F. Conway, Jr. -- Assistant General Counsel, Recreation Vehicle Industry Association

TO: Jerry R. Curry -- Administrator, NHTSA

TITLE: Federal Motor Vehicle Safety Standards; Occupant Crash Protection; Docket No. 89-22; Notice 03

ATTACHMT: Attached to letter dated 1/17/92 from Paul Jackson Rice to Edward F. Conway Jr. (A39; Std. 216)

TEXT:

The purpose of this letter is to request clarification and guidance concerning the roof crash resistance test procedures and pass/fail criterion for van conversions and motor homes with a raised roof, which are prescribed in the subject notice.

In its comments in response to Notice 01 of Docket No. 89-22, RVIA pointed out that the roof crash resistance test procedures and pass/ fail criterion for van conversions and motor homes should not be the same as those for a passenger car and urged NHTSA to develop special test procedures and a separate pass/fail criterion for these vehicles, which take into account their dissimilar physical characteristics.

For example, the prescribed roof crush resistance test device cannot be applied in the manner shown in figure 1 of standard 216 on many van conversions and motor homes that have a raised roof. Instead of impacting solely on the prescribed point, the device will also impact or "foul" the leading edge of the raised roof above and behind that point.

Also, the roof crash test pass/fail criterion for van conversions and motor homes should not be the same as that prescribed for a subcompact and other passenger cars.

In a typical full size passenger car, the floor to roof height is approximately 45 inches and distance between the head of a 50th percentile male seated in the driver's seat and the roof interior surface is approximately 6 inches. In smaller passenger cars, there is often considerably less head room.

However, in a van conversion or a motor home, the floor to roof height may be as much as 76 inches and the head of the 50th percentile male could be as much as 36 inches from the roof. Nevertheless, the roof crash resistance test device still may not depress the roof structure of these vehicles more than the FIVE INCHES allowed for a passenger car roof structure.

Thus, a van conversion or motor home with a roof elevated sufficiently to allow occupants to stand upright would fail the roof crush resistance test if its roof structure was depressed more than five inches, despite the fact its depressed roof structure remains well above the heads of seated occupants!

In the subject Notice, NHTSA did not resolve these issues. Instead, it merely acknowledged that these and other issues raised by commentators concerning alternative test procedures and requirements merit further consideration. NHTSA also stated that it will analyze these issues further and may propose amendments to the test procedure.

In the meantime, we respectfully request that NHTSA provide clarification and guidance concerning the roof crush resistance test procedures and the pass/fail criterion for van conversions and motor homes with a raised roof.