—(1) Every —
clearance lamp fitted on or to a public service vehicle under rule 12; or
pass lamp or flank lamp fitted on or to a public service vehicle or goods vehicle respectively in accordance with the Schedule,
which is capable of emitting a diffused light shall, if circular, have an illuminated area not less than 50 millimetres in diameter or, if not circular, have an illuminated area not less than the area of a circle of 50 millimetres in diameter and of such a shape that a circle of 20 millimetres in diameter may be inscribed therein.
(2) The total rated wattage of the bulb or bulbs with which a front lamp, flank lamp, clearance lamp or pass lamp referred to in paragraph (1) is fitted shall be not less than 5 watts or not more than 7 watts.
(3) Notwithstanding paragraph (1), every rear lamp of the following vehicles shall have an illuminated area of not less than the area of a circle of 88 millimetres in diameter or 60 square centimetres:
a public service vehicle registered on or after 1st July 1980, with a carrying capacity of more than 14 persons excluding the driver; and
a goods vehicle registered on or after that date with an unladen weight exceeding 1,500 kilograms.