Interpretation ID: nht93-3.48

DATE: May 17, 1993

FROM: Ray Kesler -- Kesler Research Enterprises, Ltd.

TO: John Womack -- Acting Chief Counsel, NHTSA

COPYEE: Lawrence Hufstedler

TITLE: None

ATTACHMT: Attached to letter dated 7/2/93 from John Womack to Ray Kesler (A41; Std. 111)

TEXT:

Mr. Hufstedler and I would like to thank you for your letter of April 27, 1993. It clarified many things for us which heretofore we had been unsure of, however, there is still one area which is not clear to us.

The enclosure you included in your letter was the Federal Register (in part) of September 2, 1982, which addresses FMVSS 111 rear-view mirrors. Section s571.111 states that a deviation of 12.5 percent, plus or minus, from the average radius of curvature, is allowable.

Although a method of calculating the radius of curvature is specified in section s12.1 - s12.8, it is not clear how the average radius of curvature is arrived at.

We would greatly appreciate it if your office could tell us the maximum amount of deviation we would be a owed from the bottom end of the standard (i.e.: 35" ROC), as well as perhaps explain the method by which the average radius of curvature is arrived at.

This information would be of great help to us in our continuing effort to save lives and property damage through the installation and use of our mirror.