Interpretation ID: Will_ltr

Mr. Kent Will
Project Engineer
Oshkosh Truck Corporation
2307 Oregon Street
P.O. Box 2566
Oshkosh, WI 54903-2566

Dear Mr. Will:

This is in reply to your letter asking two questions regarding the rearview mirror requirements in Federal Motor Vehicle Safety Standard (FMVSS) No. 111, Rearview mirrors.

You have stated that you have selected a mirror to be installed as an outside, rearview mirror on a truck weighing between 7,575 and 15,773 kilograms (kg). You indicate that the mirror has a radius of curvature of 2,200 millimeters and that it provides a reflective surface area of 526.6 square centimeters. You ask whether this mirror would be considered a convex mirror and, if so, whether it would be subject to the labeling and radius of curvature requirements for convex mirrors contained in Paragraphs S5.4.2 and S5.4.3 of FMVSS No. 111.

The term "convex mirror" is defined as "a mirror having a curved reflective surface whose shape is the same as that of the exterior surface of a section of a sphere." 49 CFR 571.111 (S4. Definitions). You have described your mirror as having both a "radius of curvature" and a "reflective surface." Therefore, assuming that the shape of your mirror is spherical, it would be considered a convex mirror as defined in FMVSS No. 111. The next question to be addressed is which set of performance requirements applies to the mirror in question. The answer to that question depends on the type and weight of the vehicle receiving the mirror.

You have indicated that the mirror in question will be installed on a truck. FMVSS No. 111's performance requirements for rearview mirrors installed on trucks vary according to the gross vehicle weight rating (GVWR) of the particular truck involved. Given that you intend to install the mirror on a truck with a GVWR between 7,575 kg and 15,773 kg, the applicable performance requirements are found in Paragraphs S7 and S8. The requirements in Paragraph S7 apply to trucks with a GVWR between 4,536 kg and 11,340 kg and the requirements in Paragraph S8 apply to trucks with a GVWR of 11,340 kg or more. Considering that the rearview mirror performance requirements in these two paragraphs are identical, though, it is not necessary for the purposes of this interpretation to differentiate between trucks with a GVWR between 7,575 kg and 11,340 kg and those with a GVWR between 11,340 kg and 15,773 kg.

Both paragraphs require trucks to "have outside mirrors of unit magnification, each with not less than 323 [square centimeters] of reflective surface, installed with stable supports on both sides of the vehicle." Both paragraphs also indicate that the mirrors must "be located to provide the driver a view to the rear along both sides of the vehicle and [must] be adjustable both in the horizontal and vertical directions to view the rearward scene." 49 CFR 571.111.

A "unit magnification mirror" is defined, in relevant part, as a "plane or flat mirror with a reflective surface through which the angular height and width of the image of an object is equal to the angular height and width of the object when viewed directly at the same distance." 49 CFR 571.111 (S4. Definitions.) Considering that your mirror appears to be a convex mirror, it would not be not flat enough to qualify as a mirror of unit magnification. Accordingly, installing such a mirror as an outside, rearview mirror on a truck with a GVWR between 7,575 kg and 15,773 kg would fail to satisfy the requirements of S7/S8 unless it was a supplemental mirror, installed in addition to a complying mirror.

I note that, in your letter, you ask about the labeling and radius of curvature requirements for convex mirrors found in paragraphs S5.4.2 and S5.4.3. These requirements are only relevant to passenger cars and trucks with a GVWR of 4,536 kg or less. If you have any questions, you may contact Robert Knop of this Office at (202) 366-2992.

Sincerely,

John Womack
Acting Chief Counsel

ref:111
d.8/22/01