58.—(1) In these Regulations a “variable message sign” means a device capable of displaying, at different times, two or more aspects falling within the following descriptions—
(a)a sign shown in a diagram in Schedule 1, 2, 3, 4, 5, 7, 11 or 12;
(b)a legend of a type shown in Schedule 15 in accordance with the provisions of that Schedule;
(c)a non-prescribed temporary sign as defined by regulation 53(2)(b);
(d)a blank grey or a blank black face.
(2) A variable message sign shall be of a size appropriate to display the messages referred to in sub-paragraphs (a) and (b) of paragraph (1), having regard to the normal speed of traffic on the road on or near which the sign is situated.
(3) If the construction or method of operation of a variable message sign prevents a sign from being displayed in the colours shown for it in the appropriate diagram in Schedule 1, 2, 3, 4, 5, 7 or 12, a black legend or symbol on a white or yellow background may be displayed as a white, off-white or yellow legend or symbol on a dark background, provided that any red triangle or red circle forming part of the sign is included.
(4) A legend or symbol as mentioned in paragraph (3) may be in the form of a white, off-white or yellow outline of the legend or symbol.
(5) The size of any symbol or legend, including any red triangle or circle, displayed on a variable message sign, which is displayed by means of light-emitting characters or symbols, may be varied so that the size of the symbol or legend appears to road users to be the same as it appears to them to be when it is not displayed in this manner.
(6) When a variable message sign displays—
(a)the sign shown in diagram 670;
(b)any sign shown in a diagram in Part I of Schedule 11 except diagrams 6006.2, 6008.1, 6009.3 and 6012; or
(c)a legend of the type shown in Schedule 15,
it may also display four lamps, which are of the size, colour and type specified in regulation 46(7) and have a rate of flashing of not less than 60 nor more than 150 flashes per minute, and the distance between the lamps shall accord with the overall size of the variable message sign.
(7) Where a variable message sign displays by means of light-emitting characters or symbols—
(a)the sign shown in diagram 504.1, 505.1, 506.1, 507.1, 510, 512, 512.1, 512.2 or 513; or
(b)the sign shown in diagram 670 (when showing the numerals “20”, “30”, “40” or “50”) in such a way that the sign is only visible when associated equipment detects the presence of a vehicle exceeding the speed limit indicated by the sign,
the variable message sign may display, beneath the sign displayed on it, the legend “SLOW DOWN” in characters having a height not less than one quarter of the height of the displayed sign.
(8) The display of a blank black or grey face on a variable message sign accompanied by four flashing lamps of the kind mentioned in paragraph (6) shall indicate to drivers that they should take special care.
(9) A variable message sign which displays alternately the signs shown in diagrams 7023 and 7024 shall be manually operated.