Interpretation ID: nht88-2.41

TYPE: INTERPRETATION-NHTSA

DATE: JUNE 2, 1988

FROM: C. W. PIERSON -- LORD AND PIERSON

TO: ERIKA Z. JONES -- CHIEF COUNSEL, DOT

TITLE: DOT REQUIREMENTS FOR TESTING OF SEATS (AUTOMOTIVE, TRACK, BUS, MASS TRANSIT).

ATTACHMT: LETTER DATED 10-17-88 TO CHARLES W. PIERSON FROM ERIKA Z. JONES, CHIEF COUNSEL, NHTSA

TEXT: Lately the government has been requiring more "dynamic" testing over "static" testing. This leads to broad interpretation (or mis-interpretation) by engineers like myself, and I think the loopholes should be closed.

For example, if you say a headrest shall be pull-tested at a load of 200 pounds (49USC-202-S4-b4ii) it leaves very little to the imagination. But if you say ". . . during the 10 g deceleration the H.I.C. number shall not exceed 400 for passengers ran ging in size from a six year old through a 95 percentile male" (49USC-1601-2.3.2.4-1), you set up a number of variables.

1. Are you using Dreyfus' (M.I.T.) standard man, or NASA's standard man? (Personally J use Barnes standard man-he is between the two). Have you visited a 6th grade class lately to see the size spread? I chaperoned a recent Chicago trip and the age r ange was 10 through 14!

2. The University of Michigan crash tests, but will NOT certify the results.

3. Laws requiring certification usually do not require the actual crash test to be performed.

4. Where do I get SAE Recommended Practice J833? It is NOT readily available!

5. The Formula:

(SEE ILLUSTRATION ON ORIGINAL)

. . . really can be mis-calculated and the results mis-interpreted, because you are putting variables in.

As you can see, a fixed number eliminates guesswork. Anyone can understand it, and over the years I've reached the conclusion that only about half of the engineers have a real live college degree, (I'm a Western grad!)