Document ID: chunk:federal_register_of_legislation:F2023C00133:body:0:p4
Version: federal_register_of_legislation:F2023C00133
Segment Type: other
Provision Reference: 
Character Range: 10426–13821

only vertical and horizontal planes shall be used;
4.22.5.                          'Apparent surface' for a defined direction of observation means the orthogonal projection of the light-emitting surface on a plane perpendicular to the direction of observation;
4.23.                                'Centre of Reference' means the intersection of the axis of reference with the light-emitting surface; it is specified by the manufacturer of the lamp;
4.24.                                'Angles of Geometric Visibility' means the angles which determine the minimum solid-angle zone in which the apparent surface of the lamp must be visible; this solid-angle zone is defined by the segments of the sphere of which the centre coincides with the 'Centre of Reference' of the lamp and the equator is parallel to the ground; these segments are determined in relation to the axis of reference; the horizontal angles beta correspond to the longitude and the vertical angles alpha to the latitude. There must be no obstacle on the inside of the angles of geometric visibility to the propagation of light from any part of the apparent surface of the lamp. No account is taken of obstacles existing at the time of approval, where required, of the lamp;

         4.25.                                '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 of:

4.25.1.                          rear-view mirrors;
4.25.2.                          side 'Direction Indicator Lamps';
4.25.3.                          'Front Position (Side) Lamp' and 'Rear Position (Side) Lamp';
4.25.4.                          'End-outline Marker Lamps';
4.25.5.                          'Parking Lamps';
4.25.6.                          'Reflex Reflectors';
4.25.7.                          tyres nearest their point of contact with the ground;
4.25.8.                          connections for tyre-pressure gauges; and
4.25.9.                          any anti-skid devices mounted on the wheels.
4.26.                                'Distance between two lamps which face in the same direction', the distance between the orthogonal projections in a plane perpendicular to the axes of reference of the outline of the two 'Illuminating Surfaces';
4.27.                                'Operating Tell-tale' means a light or auditory device showing that a device has been switched on and is operating correctly or not;
4.28.                                'Circuit-closed Tell-tale' means a light showing that a device has been switched on, but not showing whether it is operating correctly or not;
4.29.                                'Optional Lamp' means a lamp, the presence of which is left to the discretion of the manufacturer;
4.30.                                'Concealable Illuminating Lamp' means a headlamp capable of being partly or completely hidden when not in use. This result may be achieved by means of a movable cover, by movement of the headlamp, or by any other suitable means; the term "vanishing lamp" is used more particularly to describe a lamp which, by its movement, can be concealed inside the bodywork;
4.31.                                Single and Multiple Lamps:
4.31.1.                          A 'Single Lamp' also means any