Interpretation ID: nht87-2.9

TYPE: INTERPRETATION-NHTSA

DATE: 06/12/87

FROM: AUTHOR UNAVAILABLE; Erika Z. Jones; NHTSA

TO: Mr. Thomas D. Turner

TITLE: FMVSS INTERPRETATION

TEXT:

Mr. Thomas D. Turner Manager Engineering Services Blue Bird Body Company P.O. Box 937

Dear Mr. Turner:

Thank you for your letter concerning Standard No. 301, Fuel System Integrity. You stated that there is a conflict in the standard about the correct ground clearance of the contoured impact surface used in the school bus impact test of the standard. You s tated further that S7.5.1 of the standard refers to the dimension between the ground to the lower edge of the impact surface as 5.25 + 0.5 inches, while Figure 2 of the standard shows the ground clearance to be 12.25. As discussed below, and as Mr. Oesch of my staff discussed with you in a phone call earlier this year, the correct dimension is 5.25 + 0.5 inches.

As you noted in your letter, the agency adopted the use of the contoured barrier in a final rule issued on April 16, 1975. The preamble to that final rule stated that "The contoured barrier would incorporate the moving barrier specifications of SAE Recom mended Practice J972a (March 1973). However, the impact surface of the barrier would be at a height 30 inches above the ground level, rather than 37 inches as specified in the SAE provision. Studies have shown that a 30-inch test height is more represent ative of actual collisions. This would be a typical engine height of vehicles that might impact a schoolbus." Thus, in S7.5.1 of the standard, the agency adopted the ground clearance as 5.25 inches + 0.5 inches to ensure that the top of the barrier would be 30 inches from the ground. In Figure 2, the agency apparently incorporated the barrier dimensions directly from the SAE Recommended Practice J972a, without changing the ground clearance dimension.

We will publish an amendment to the standard that will correct the ground clearance dimension set out in Figure 2 of Standard No. 301. Thank you for bring this matter to the agency's attention.

If you have any further questions, please let me know.

Sincerely,

Erika Z. Jones Chief Counsel

November 20, 1986

Ms. Erika Z. Jones Chief Counsel National Highway Traffic Safety Administration 400 7th Street, S.W. Washington, D.C. 20590

Reference: 49 CFR Part 571; 3O1-75 Fuel System Integrity

Section S7.5.1 of the standard specifies . . ." The contoured impact surface which is 24.75 inches high and 78 inches wide, conforms to the dimensions shown in Figure 2, and is attached to the carriage as shown in that figure. The ground clearance to the lower edge of the impact surface is 5.25 + 0.5 inches"...

Figure 2 shows dimension D, ground clearance to the lower edge of the impact surface, is 12.25 inches while the text says it is 5.25 + 0.5 inches.

In reviewing the history of Standard 301-75, I found the height of the impact surface was specifically discussed in Federal Register Volume 40, Number 74, Wednesday, April 16, 1975, with regard to school buses. The highlighted areas on the attached copy of this discussion indict the intention was to use the 5.25 inch dimension, making the overall height of the impact surface 30 inches, for school bus moving contoured barrier crash tests.

Based on this history and recent discussions with NHTSA personnel, it is our understanding that the 5.25 + 0.5 inches is the correct dimension and dimension D in Figure 2 should be corrected to show this value. Please confirm that our understanding is co rrect. We are currently obtaining quotations from test laboratories for FMVSS 301 Certification testing and must have this issue resolved before finalizing testing plans. If written confirmation can be provided by December 11, 1986, it would be appreciat ed. If not, please have one of your staff verbally advise us by December 11, 1986, and then follow-up with a letter of confirmation. Thank you for a timely response to this request.

Very truly yours,

Thomas D. Turner Manager Engineering Services

fvc/1839

c: FHVSS 301-75

(SEE ATTACHMENT...)