The Pelican Pedestrian Crossings Regulations and General Directions 1987

Vehicular light signals

2.  The vehicular light signals shall be as follows–

(a) three lights shall be used, one red, one amber, and one green;

(b) the lamps showing the aforesaid lights shall be arranged vertically, the lamp showing the red light being the uppermost and that showing the 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 millimetres nor more than 220 millimetres;

(d) the height of the centre of the amber lens from the surface of the carriageway in the immediate vicinity shall, in the case of signals placed at the side of the carriageway or on a central reservation, be not less than 2.4 metres nor more than 4 metres and, in the case of signals placed elsewhere and over the carriageway, not less than 6.1 metres nor more than 9 metres;

(e) the centres of the lenses of adjacent lamps shall be not less than 305 millimetres nor more than 360 millimetres apart;

(f) the lamp showing the amber light shall be capable of showing a steady light or a flashing light such that it flashes at a rate of not less than 70 nor more than 90 flashes per minute; and

(g) no lettering or symbols shall be used upon the lens.