Lamps to be lit during hours of darkness
5.—(1)  When any motor vehicle is in motion during the hours of darkness on a length of road, every lamp required to be carried by the motor vehicle by virtue of these Rules shall be kept lit.
(2)  Every headlamp of a vehicle shall, when lit under paragraph (1), emit a dipped beam if —
(a)there are on the road along which the vehicle is moving street lamps placed not more than 150 metres from each other; and
(b)the lamps are lit.
(3)  For the purposes of this rule, it shall not be necessary for the front lamps of a vehicle to be kept lit if the vehicle is being drawn by another and the distance between the two vehicles is less than 1½ metres.