(Regulations 18 and 20)
1. A dim-dip device fitted to satisfy regulation 18 shall cause light to be emitted from the dipped-beam filament of each obligatory dipped-beam headlamp, each such light having, so far as is practicable, an intensity of between 10 and 20 per cent of the intensity of the normal dipped beam.
2. Running lamps fitted to satisfy regulation 18 shall be in the form of a matched pair of front lamps, each of which–
(a)is fitted in a position in which an obligatory front position lamp may lawfully be fitted, and
(b)is capable of emitting white light to the front having an intensity of not less than 200 candelas, measured from directly in front of the centre of the lamp in a direction parallel to the longitudinal axis of the vehicle, and of not more than 800 candelas in any direction.
3. The electrical connections to the obligatory dim-dip device or running lamps, as the case may be, shall be such that the light output specified in paragraph 1 or 2 above is emitted automatically whenever–
(a)the engine of the vehicle is running, or the key or devices which control the starting or stopping of the engine are in the normal position for driving the vehicle, and
(i)the obligatory position lamps, but not the headlamps, of the vehicle are switched on, or
(ii)the obligatory position lamps are switched off.
There is no requirement relating to an optional dim-dip device or an optional running lamp.