(d) If the sign shown in diagram 561 has an area of 180 square centimetres, that Sign shall be illuminated by the method prescribed at sub-paragraph (c)(ii) above and not otherwise; but if that sign so shown has an area of less than 180 square centimetres and no less than 45 square centimetres, then it shall be illuminated either by the use of a single rectangular reflector of the corner cube type extending over the whole surface of the sign or by the method prescribed at sub-paragraph (c )(iv) above but by no other method.
(3) The colour reflected by the sign shown either in diagram 560 or in 561 shall be red when the sign indicates the edge or the left hand side or the carriageway or an obstruction near that edge and shall be white when the sign indicates the edge of the right-hand side or the carriageway or an obstruction near that edge, unless the sign indicates the edge of the right—hand side or the carriageway of a dual-carriageway road or an obstruction near that edge when the said colour so reflected shall be amber.
18.—(1) Nothing in this Regulation shall apply in the signs shown in diagrams 536, 560, 561 and 828.1.
(2) Subject to the provisions or Regulation 15 and paragraph (1) above any sign shown in a diagram in Schedule 1 may be illuminated by the use of reflecting material in accordance with the following provisions of this Regulation.
(3) Subject to paragraph (4) where reflecting material is used on any sign shown in a diagram in Schedule 1 it shall be of the same colour as that or, and extend throughout that part of the sign to which it is applied:
Provided that no reflecting material shall be applied to
(a) any part of a sign coloured black.
(b) any part of the sign shown in diagram 505.1 which is coloured fluorescent yellow unless the reflecting material is applied to that part in horizontal strips each such strip being 3 millimetres wide, spaced at intervals of 6 millimetre: from each other, the centre or the sign being located at 3 point in one such interval equidistant from the strips so spaced.
In this paragraph the word "part" in relation to a sign means any part of the surface of that sign uniformly coloured and bounded by parts of a different colour.
(4)(a) Where in accordance with the last paragraph, different colours or reflecting material are used next to one another on the same sign being a traffic sign to which this paragraph applies in accordance with the next following sub-paragraph, a gap of not more than 20 millimetres in width may by left between the different colours of reflecting material.
(b) This paragraph applies only to traffic signs which being circular in shape have a diameter of at least 1.2 metres, being triangular in shape have a height of at least 1.2 metres along the perpendicular from apex to base, or being rectangular in shape have a side which is at least 1.2 metres in length.
