31.—(1) Light signals may be used for the control of vehicular name and shall be of the size, colour and type prescribed by paragraph (2), by paragraph (3) or by paragraph (4).
(2) The size, colour and type of light signals prescribed by this paragraph shall be as follows:—
(a) three lights shall be used, 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 195 nor more than 220 millimetres unless the lens is a lens of the kind shown in diagram 3001 when instead the said diameter may be not less than 290 nor more than 310 millimetres;
(d) the height of the centre of the amber lens from the surface of the carriageway in the immediate vicinity shall be in the case of signals placed at the side or the carriageway or on a street refuge not less than 2.4 nor more than 4 metres and in the case or signals placed elsewhere and over the carriageway not less than 6.1 nor more than 9 metres;
(e) the centres of adjacent lenses shall be not less than 305 nor more than 350 millimetres apart;
(f) no lettering shall be used upon the lenses or in connection with a light signal;
(g) the sequence of the lights shown for the purpose of controlling vehicular traffic shall be as follows.—
(i)red,
(ii)amber and red together,
(iii)green,
(iv)amber.
(3) The size, colour and type or light signals prescribed try this paragraph shall be as follows:—
(a) Four lamps each showing an intermittent red light shall be used.
(b) The lamps shall be so fitted as to enclose a rectangular area bounded by the one pair of sides extending horizontally and terminating as to each side in the centres of each pair of lenses (in these Regulations called "the horizontal pairs") and by the other pair of sides extending vertically in relation to the ground and terminating as to each side in the centres of each pair of lenses (in these Regulations called "the vertical pairs").
(c) When the four lamps are erected beside the carriageway, the distance between the centres of the lenses for each of the horizontal pairs shall be not less than 945 nor more than 955 millimetres and for each of the vertical pairs shall be not less than 695 nor more than 705 millimetres in accordance with the arrangement shown in diagram 6032.
(d) When the four lamps are erected over the carriageway, the distance between the said centres for each or the horizontal pails shall be not less than 1395 nor more than 1405 millimetres and for each or the vertical pairs not less than 545 nor more than 555 millimetres in accordance with the arrangement shown in diagram 6031.
