Mr. Kiminori Hyodo
Deputy General Manager, Regulation & Certification
Koito Manufacturing Co., Ltd.
Dear Mr. Hyodo:
This is in response to your letter, in which you asked about the origin of the required visibility angle in Figure 20 of Federal motor vehicle safety standard (FMVSS) No. 108, Lamps, Reflective Devices, and Associated Equipment. Specifically, you ask whether the origin of the visibility angle for FMVSS No. 108, Figure 20 is identical to that described in Economic Commission for Europe (ECE) R.48, i.e., the intersection of the axis of reference with the exterior lens of the lighting device. As discussed below, our answer is no. It is our opinion that the referenced Society of Automotive Engineers (SAE) standard (SAE J575e) makes clear that the photometric measurement is made at a distance between the light source of the lighting device and the point of measurement specified for the lighting device, and in the case of the filament light sources you have provided as examples, the light source of the device is the filament itself. Thus, the measurement is made from the filament center, and not from the exterior lens.
By way of background, the National Highway Traffic Safety Administration (NHTSA) is authorized to issue FMVSSs that set performance requirements for new motor vehicles and items of motor vehicle equipment (see 49 U.S.C. Chapter 301). NHTSA does not provide approvals of motor vehicles or motor vehicle equipment. Instead, manufacturers are required to self-certify that their products conform to all applicable safety standards that are in effect on the date of manufacture. NHTSA selects a sampling of new vehicles and equipment each year to determine their compliance with applicable FMVSSs. If our testing or examination reveals an apparent noncompliance, we may require the manufacturer to remedy the noncompliance, and may initiate an enforcement proceeding if necessary to ensure that the manufacturer takes appropriate action.
Our August 11, 2004 Final Rule (2004 Final Rule) amended the visibility requirements of FMVSS No. 108 and consolidated all the visibility requirements in a new paragraph, S5.3.2. 69 Fed. Reg. 48805. As you pointed out in your letter, S5.3.2(b)(2) states that [w]hen a vehicle is equipped with any lamp listed in Figure 20 of this standard, each such lamp must provide a luminous intensity not less than specified in Figure 20 in any direction throughout the pattern defined by the corner points specified in Figure 20 for each such lamp. The luminous intensity must be measured in accordance with the photometry test requirements of the applicable SAE Standards and Recommended Practices incorporated by reference or sub-referenced in this standard. As you further pointed out in your letter, SAE J575e (Tests for Motor Vehicle Lighting Devices and Components) is incorporated by reference in FMVSS No. 108, and states that the photometric measurement shall be made at a distance between the light source and the point of measurement specified for the lighting device. SAE J575e goes on to define the V axis as the line formed by the intersection of a vertical plane through the light source of the device This indicates that the light source is the origin of the beam in a lighting device, or, in the devices you gave as illustrative examples in your letter, the filament center.
Moreover, while the 2004 Final Rule sought to improve compatibility of our lighting requirements with those of the [ECE], the new geometric visibility requirements you seek clarification on did not entirely harmonize FMVSS No. 108 with ECE R.48. In the 2004 Final Rule, the agency recognized that one of the many ways ECE R.48 visibility requirements differed from FMVSS No. 108 requirements was that ECE R.48 contains a definition for angles of geometric visibility, whereas the specifications for lighting tests in FMVSS No. 108 are all in SAE J575e, which is incorporated by reference. 69 Fed. Reg. 48805, 48806. In your letter, you suggest that since the new luminous intensity method Figure (Figure 20) was introduced to increase compatibility with ECE, the origin of the visibility angle for Figure 20 is identical to that described in ECE R.48. We disagree. Since NHTSA declined to adopt ECE R.48s definition of angles of geometric visibility in the 2004 Final Rule, we effectively retained the photometry measurements as specified in SAE J575e. Accordingly, we believe that the angles of measurement required in Figure 20 are to be measured from the light source of the lighting device, and in the lighting devices you have provided as illustrative examples, the measurement should be made from the filament center.
If you have any further questions, please do not hesitate to contact Sarah Alves of my staff at (202) 366-2992.
Anthony M. Cooke