Interpretation ID: nht90-3.92

TYPE: Interpretation-NHTSA

DATE: September 10, 1990

FROM: Paul Jackson Rice -- Chief Counsel, NHTSA

TO: David G. Dick Acts Testing Labs, Inc.

TITLE: None

ATTACHMT: Attached to letter dated 2-20-90 from D.G. Dick to NHTSA (OCC 4452)

TEXT:

This responds to your letter asking about the head impact protection requirements set forth in paragraph S5.2.3.2(a) of Standard 213, Child restraint systems. I regret the delay in responding.

Paragraph S5.2.3.2(a) states that certain energy absorbing material used to cover child seat surfaces must have a 25 percent compression-deflection resistance of not less than 0.5 and not more than 10 pounds per square inch (psi). You ask whether a valu e slightly less than 0.5 (such as the 0.47 psi example you provided) would be rounded to 0.5 psi. If rounding were permitted, you point out that the rounded value would meet the 0.5 psi requirement of S5.2.3.2(a).

The answer to your question is no, NHTSA would not round the value to 0.5 psi when testing the child seat. Rounding is generally not used in the safety standards. The standards expressly specify when rounding is appropriate. Standard 222, School bus p assenger seating and crash protection, specifies that the number of seating positions in a school bus bench seat (S4.1) is determined by rounding. In view of the express reference to rounding in some safety standards, and since S5.2.3.2(a) does not expr essly state rounding is appropriate, the value for the compression-deflection resistance would not be rounded.

You also ask whether there is any situation in which a value of less than 0.5 psi would be acceptable. The answer is "no." The minimum of 0.5 psi is required by S5.2.3.2(a) for restraints (other than a harness) recommended for children weighing less th an 20 pounds. Any value less than the minimum required value is a noncompliance.

Your last question asks about the reasons for the 0.5 psi minimum. In the agency's notice adopting the compression-deflection requirements, the agency indicated that those requirements would allow the use of a wide range of materials which should enable manufacturers to provide protective padding without cost increases. A copy of that notice is enclosed for your information.

I hope this information is helpful. Please contact us if you have further questions.