Document ID: chunk:federal_register_of_legislation:F2023C00136:reg:113:p5
Version: federal_register_of_legislation:F2023C00136
Segment Type: reg
Provision Reference: reg 113 (pt 5/21)
Character Range: 28487–31286

by the edges of screens situated in this plane, each allowing only 98 per cent of the total luminous intensity of the light to persist in the direction of the axis of reference. To determine the lower, upper and lateral limits of the illuminating surface, only screens with horizontal or vertical edges shall be used;
2.7.3. "Illuminating surface of a retro-reflector" (para. 2.5.13. above) means the orthogonal projection of a retro-reflector in a plane perpendicular to its axis of reference and delimited by planes continuous to the outermost parts of the retro-reflector's optical system and parallel to that axis. For the purposes of determining the lower, upper and lateral edges of the device, only horizontal and vertical planes shall be considered;
2.8. The "apparent surface" for a defined direction of observation means, at the request of the manufacturer or his duly accredited representative, the orthogonal projection of:
Either the boundary of the illuminating surface projected on the exterior surface of the lens (a-b),
Or the light-emitting surface (c-d),
In a plane perpendicular to the direction of observation and tangential to the most exterior point of the lens (see Annex 3 to this Regulation);
2.9. "Axis of reference" (or "reference axis") means the characteristic axis of the lamp determined by the manufacturer (of the lamp) for use as the direction of reference (H = 0°, V = 0°) for angles of field for photometric measurements and for installing the lamp on the vehicle;
2.10. "Centre of reference" means the intersection of the axis of reference with the exterior light-emitting surface; it is specified by the manufacturer of the lamp;
2.11. "Angles of geometric visibility" means the angles, which determine the field of the minimum solid angle in which the apparent surface of the lamp shall be visible. That field of the solid angle is determined by the segments of the sphere of which the centre coincides with the centre of reference of the lamp and the equator is parallel with the ground. These segments are determined in relation to the axis of reference. The horizontal angles β, correspond to the longitude and the vertical angles α to the latitude;
2.12. "Extreme outer edge", on either side of the vehicle means the plane parallel to the median longitudinal plane of the vehicle and touching the lateral extremity of the vehicle, disregarding the projection or projections:
2.12.1. Of rear-view mirrors,
2.12.2. Of direction indicator lamps,
2.12.3. Of front and rear position lamps and retro-reflectors;
2.13. "Over-all width" means the distance between the two vertical planes defined in paragraph 2.12. above;
2.14. "A single lamp" means:
             (a) A device or part of a device having one lighting or light-signalling function, one or more light