Interpretation ID: aiam4597
DC 20515;
"Dear Mr. Panetta: This letter responds to your inquiry on behalf o your constituent, Mr. Botelho. You asked whether Federal regulations require mirrors to be placed on the right side of vehicles and whether such mirrors must be convex in nature. Mr. Botelho expressed his objection to requiring convex mirrors, because he believes convex mirrors distort images and cause objects to appear further away than they actually are. I am pleased to have this opportunity to explain this requirement and its background for you. Standard No. 111, Rearview Mirrors (49 CFR /571.111, copy enclosed)) establishes performance and location requirements for the rearview mirrors installed in new vehicles. Specifically, a passenger car whose inside rearview mirror does not meet the field of view requirements of section S5.1.1 must have an outside mirror on the passenger side of either unit magnification or a convex mirror. In a September 2, 1982 final rule amending Standard No. 111, the National Highway Traffic Safety Administration (NHTSA) explained that convex mirrors offer safety benefits by providing an expanded field of view to the rear, thereby reducing the need for the driver to turn around to view the rear directly. On the other hand, some users of convex mirrors that were used to the images shown by conventional plane mirrors incorrectly perceived that the object shown in the convex mirror was further to the rear than it actually was. Additionally, some users of convex mirrors experienced double vision, eyestrain, and nausea. After considering these potential advantages and disadvantages, NHTSA amended Standard No. 111 so that it does not require any vehicle to be equipped with convex mirrors, but it permits the use of convex mirrors on the passenger side of cars and light trucks, provided that the convex mirror meets certain additional requirements. The additional requirements applicable to convex mirrors on the passenger side of cars and light trucks are: 1. A maximum radius of curvature for the convex mirror. This limits the range of convexities to which drivers will be exposed. It also ensures that the field of view will be noticeably greater than for a plane mirror. 2. A minimum radius of curvature for the convex mirror. This ensures that the image size in the convex mirror will be adequate and distortion will not be excessive. 3. A stringent maximum permissible variation in the radius of curvature over the surface of the convex mirror. This requirement, which is more stringent than the European requirement in this area, also ensures that convex mirrors will have low distortion. 4. A warning etched on the convex mirror that objects shown in the mirror are closer than they appear. This requirement ensures that the driver who may not be familiar with convex mirrors will not be misled by the image size of the convex mirror and the apparent distance to the object. Hence, we agree with Mr. Botelho that the areas he has identified are potential problems unique to convex mirrors. However, our standard includes special requirements for convex mirrors to minimize the potential problems identified by Mr. Botelho and other potential problems that were identified in research studies of convex mirrors. We are not aware of any data showing that convex mirrors that comply with those special requirements present any unacceptable problems for drivers. I hope this information is helpful. If you have any further questions or need any additional information on this subject, please let me know. Sincerely, Erika Z. Jones Chief Counsel Enclosure";