any combination of two or more lamps, whether identical or not, having the same function and emitting light of the same colour, if it comprises devices, the projection of whose aggregate light-emitting surfaces in a given transverse plane occupies 60 % or more of the area of the smallest rectangle circumscribing the projections of those light-emitting surfaces, provided that such combination is, where approval is required, approved as a single lamp. This possible combination does not apply to main-beam headlamps, dipped-beam headlamps and front fog lamps.