Interpretation ID: 3081o
404 Williams Street
Sturgis, MI 49091
Dear Mr. Pierson:
This responds to your letter in which you made several observations about dynamic testing requirements generally in our safety standards. I am pleased to have this opportunity to explain those requirements for you.
You began by observing that this agency has been moving to replace static testing requirements (tests in which individual vehicle components are subjected to specified levels of slowly applied force in a laboratory test) with dynamic testing requirements (e.g., tests in which a vehicle is crashed into a barrier and anthropomorphic test dummies are used to measure the protection provided by the vehicle to occupants in a crash). You then suggested that there were several potential difficulties or misinterpretations that could arise with dynamic testing.
First, you asked which of the several standardized human physical dimensions should be used to determine if a vehicle complies with our safety standards that refer to a specified percentile child or adult. For instance, section S7.1.1 of Standard No. 208, Occupant Crash Protection (49 CFR /571.208) requires the lap belt portion of a seat belt assembly to adjust to fit persons whose dimensions range from a 50th percentile 6 year old child to a 95th percentile adult male, while the shoulder belt portion of a seat belt assembly must adjust to fit persons whose dimensions range from a 5th percentile adult female to a 95th percentile adult male.
When our regulations refer to a specific size for a vehicle occupant, the regulations also clearly specify the dimensions and weights of the vehicle occupants to which we are referring. Section S7.1.3 of Standard No. 208 sets forth the critical weights and dimensions of all vehicle occupants referred to in that standard. The critical weights and physical dimensions for all of the anthropomorphic test dummies used to measure compliance with our safety standards are set forth in 49 CFR Part 572, Anthropomorphic Test Dummies.
Second, you noted that testing facilities will conduct crash testing, but will not certify those results. This practice on the part of the testing facilities is consistent with the requirements of the National Traffic and Motor Vehicle Safety Act (the Safety Act; 15 U.S.C. 1381 et seq.). Section 114 of the Safety Act (15 U.S.C. 1403) explicitly requires every manufacturer to certify that each of its vehicles or items of equipment conforms to all applicable safety standards. Hence, regardless of how a testing facility presents test results to a manufacturer, it is the manufacturer of the product, not the testing facility, that is statutorily responsible for certifying that each of its products complies with all applicable safety standards.
Third, you stated that "laws requiring certification usually do not require the actual crash test to be performed." You are correct to the extent that you are suggesting that the Safety Act does not require manufacturers to conduct any testing before certifying that its product complies with all applicable safety standards. The Safety Act requires only that the manufacturer exercise due care in certifying its products compliance with the safety standards. It is up to the individual manufacturer in the first instance what data, test results, computer simulations, engineering analyses, or other information it needs to enable it to certify that each of its products comply with all applicable safety standards.
However, for purposes of enforcing the safety standards, this agency conducts spot checks of products after they have been certified by the manufacturer. NHTSA purchases the products and tests them according to the procedures specified in the applicable standard. If the standard specifies a crash test, NHTSA conducts the crash test according to the specified procedures.
Fourth, you asked how you could obtain a copy of the Society of Automotive Engineers (SAE) Recommended Practice J833. This and all other SAE materials can be obtained by writing to: Customer Service Department, Publications Group, SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001. The SAE's Customer Service Department can also be contacted by telephone at (402) 776-4970.
Fifth and finally, you suggested that the formula used to calculate the head injury criterion (HIC), set forth in sections S6.1.2 and S6.2.2 of Standard No. 208, is relatively complex, so the HIC could be miscalculated. It is true that any mathematical calculation can be performed incorrectly. Nevertheless, the formula for calculating the HIC yields only one correct result for any set of variables. This agency has not experienced any difficulties in calculating the proper HIC from any test results, and is not aware of any difficulties that have been encountered by any manufacturers in making such calculations. Hence, we do not believe there are any problems associated with the HIC formula.
I hope this information is helpful. If you have any further questions or need additional information in this area, please feel free to contact me.
Sincerely,
Erika Z. Jones Chief Counsel
ref:VSA#208 d:l0/l7/88