Interpretation ID: nht76-2.19

DATE: 11/22/76

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Crown Coach Corp.

TITLE: FMVSS INTERPRETATION

TEXT: This is in response to your letter of October 7, 1976, in which you ask several questions concerning Standard No. 217 Bus Window Retention and Release, and Standard No. 222, School Bus Passenger Seating and Crash Protection.

Your first question asks whether a California regulation requiring 20-inch minimum seat spacing in school buses would be preempted by the requirement for 20-inch maximum seat spacing in Standard No. 222.

The National Traffic and Motor Vehicle Safety Act (the Act) provides in section 103(d) that any state or local law or regulation on an aspect of motor vehicle performance covered by a Federal standard must be identical to that Federal standard. Although the NHTSA requirement is phrased in terms of maximum spacing while the California standard concerns minimum spacing, the aspect of performance in question is seat spacing. Therefore, it is the NHTSA's opinion that a California standard on seat spacing regulates the same aspect of performance and to the degree it is not identical to the Federal standard, it would be preempted.

Your second question asks whether the seating reference point, as specified in relation to the "H" Point used in SAE Standard J826b, varies with the size of different individuals. The seating reference point, as defined by the NHTSA in Part 571.3 allows the manufacturer some discretion in selecting a point that approximates the position of the pivot center of the human torso and the thigh. While the NHTSA definition does refer to the SAE procedures for "H" point location that includes the specific measurements you cite, the manufacturer retains discretion to vary this point slightly as long as he can show that the point selected continues to simulate the position of the pivot center of the human torso and the thigh of the passengers for whom the seat is designed.

Finally, you note in your letter that compliance with the seat spacing required in Standard No. 222 might entail relocation of the side emergency exit, because Standard No. 217 requires that "[a] vertical transverse plane tangent to the rearmost point of a seat back shall pass through the forward edge of a side emergency door." The seat spacing requirement arguably could occasion the realignment of the side emergency door, but this does not have to be the case. The manufacturer is free to adjust seat spacing to be properly aligned with the emergency exit. The NHTSA's intent in this requirement is to provide an emergency exit opening extending at least 2 feet rearward of a vertical transverse plane tangent to the rearmost point of a seat back. The agency would not prohibit the use of doors wider than 2 feet as long as a minimum 2-foot opening is provided rearward of the reference plane and the latch mechanism is operated by a device located within the required 2-foot opening.

SINCERELY, Crown COACH CORPORATION

October 7, 1976

National Highway Traffic Safety Administration Motor Vehicle Programs Office of Chief Council

SUBJECT: Federal Standard 222-School Bus Seating and Crash Protection

We are presently trying to establish a seating floor plan to conform to your standards. So far, we know of only one manufacturer that may produce a seat meeting your requirements, namely American Seating Company.

The point in question is the establishment of some manufacturing tolerance between seats. Standard 222 states the maximum spacing from the seats, Seating Reference Point (SAE "H" Point), is 20 inches. This distance is equal to the minimum California standard of 25 inches from seat back to the back of the seat in front. This would leave no manufacturing tolerance. We know that Federal Standards take precedence, but the State could put a limitation on minimum spacing. American Seating has told us that they are using 20 inches +/- 1/2 inch. as a target. They will also have a tolerance on the thickness of their seat, which would affect seat spacing.

Another question on the "H" Point as specified in SAE Standard J826 - the distance up from the seat to the "H" Point is 3.84 Inches and from the "H" Point to the seat back is 5.28 Inches. Would not these dimensions change with respect to different percentile figures?

The location of the seats and tolerances create another problem which cannot be solved until something has been firmed up; that is, the location of the side emergency exit.

Standard 217, Docket No. 75-3, Notice 4, states "A vertical transverse plane tanget to the rearmost point of a seat back shall pass through the forward edge of a side emergency door." This means the door has to float with the seat locations. Also suppose the door is larger in size than the Standard states, this would penalize the manufacturer of the bus body, having to redesign side walls to accept different door and window locations.

We have been in contact with Mr. Tim Hoyt of your Docket Writer Section, who has been very helpful, but cannot answer our specific questions, and recommends we contact your Department for clarification of the Standard and specific answers to our problems.

If you need any clarification on our questions please phone and we will try to explain more fully.

Ray Hartman Vice President-Engineering