Provided that during the hours of darkness as defined in the Road Transport Lighting Act, 1927 , red or green flags shall not be used as afore said unless they are so illuminated by lighting as to be clearly visible to approaching traffic.
27. Light signals may be used for the control of vehicular traffic subject to the following provisions:—
(a) three lights shall be used facing the stream of traffic which the signal is intended to control, one red, one amber and one green;
(b) the lamps showing the coloured lights aforesaid shall be arranged vertically, the lamp showing a red light being the uppermost and that showing a green light the lowermost;
(c) each lamp shall be separately illuminated and the effective diameter of the lens thereof shall be not less than 8 inches nor more than 8¼ inches;
(d) the height of the centre of the green lens from the carriageway shall be 7 feet 6 inches, provided that where desirable owing to road gradients this height may be increased to not more than 10 feet;
(e) the centres of the lenses shall be not more than 14 inches apart;
(f) the head of the signal enclosing the lamps, and the post, if any, on which it is supported shall be painted black and white in alternate horizontal bands;
(g) the word "STOP" in black lettering shall be placed upon the lens of the lamp showing a red light and no other lettering shall be used upon the lenses or in connection with a light signal;
(h) the sequence of the signal lights shown for the purpose of controlling vehicular traffic shall be as follows:—
(i) Red,
(ii) Amber and red together,
(iii) Green,
(iv) Amber;
Provided that any such light signal on the green lens of which the word "GO" has been placed before the coming into operation of these Regulations shall be deemed to comply with this Regulation.
28. A lens of the size and colour shown in diagram No. 1 in the Third Schedule to these Regulations which, when illuminated, shows a green arrow—
(a) may be substituted for the lens showing the green light in the light signals referred to in Regulation 27 of these Regulations in any of the methods shown in diagrams Nos. 4 to 8 inclusive in the said Schedule; or
(b) may be affixed to the light signals referred to in the said Regulation 27 or to those signals as altered in accordance with the preceding paragraph of this Regulation in any of the methods shown in diagrams Nos. 2, 3, 6, 7 and 8 in the said Schedule.
