‘geometric visibility’ means the angles which determine the square field in which the light-emitting surface of the lighting device is completely visible when the relevant angles (α vertical and β horizontal) are measured at the outward contour of the apparent surface and the lamp is observed from afar. However, if any obstacles is located within this field and partly obscuring the light-emitting surface, it may be accepted where it is proven that, even with such obstructions, the photometric values prescribed for the type-approval of the lighting device as component are complied with;

‘single (lighting device)’ means a lighting device or part of a device, having one function and one illuminating surface and one or more light sources; it may also mean any assembly of two independent or grouped lighting devices, whether identical or not, having the same function, if they are installed in such a way that the projections of the light-emitting surfaces of the lighting devices on a given transverse plane occupy not less than 60 % of the smallest rectangle circumscribing the projections of the said light-emitting surfaces;

2.1.9. No light-emitting surface of any red lamp, with the exception of rearmost side marker lamps, shall be visible towards the front and no light-emitting surface of any white lamp, with the exception of reversing lamps, shall be visible towards the rear.

Emergency exit doors to the surface and doors to technical rooms are provided with suitable locks

Emergency exit doors to the surface and doors to equipment rooms are provided with suitable locks

The light-emitting surface may be constituted by a number of juxtaposed elements on condition that the projections of the several individual light-emitting surfaces on the same transverse plane occupy not less than 60 % of the area of the smallest rectangle circumscribing the projections of those individual light-emitting surfaces.