29.—(1) Portable light signals may be used for the control of vehicular traffic—
(a) where, owing to roadworks being in progress or for some other reason the width of the carriageway is temporarily restricted so that it will carry only one line of traffic, or
(b) during the progress of temporary schemes of traffic control, if the signals are in the control of the police.
(2) Such light signals shall comply either with the provisions of sub-paragraphs (a), (b), (c), (e), (g) and (h) of Regulation 27 of these Regulations and sub-paragraphs (d) and (f') of paragraph (3) of this Regulation or with all the provisions of the said paragraph (3).
(3) (a) Two lights shall be used facing the stream of traffic which the signal is intended to control, one red and the other green;
(b) the lamps showing the coloured lights aforesaid shall be arranged vertically, the lamp showing a red light being uppermost;
(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 84 inches;
(d) the height of the centre of the green lens from the carriageway shall be not less than 5 feet nor more than 7 feet 6 inches;
(e) the centres of the lenses shall be not more than 28 inches apart;
(f) the signal head and the post or legs 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 where the signals are in the control of the police appropriate words indicating that the signals are police signals may be used; and
(h) the red and green lights shall not be shown together and one shall follow the other without any appreciable interval of time.
30.—(1) The significance of the light signals prescribed by Regulation 27 or 29 of these Regulations shall be as follows:—
(a) the red signal shall convey the prohibition that vehicular traffic shall not proceed beyond the stop line on the carriageway provided in conjunction with the signals or, if there is no stop line, beyond the signals;
(b) the amber-with-red signal (where an amber signal is provided ) shall be taken to denote an impending change in the indication given by the signal from red to green but shall not alter the prohibition conveyed by the red signal;
(c) the green signal shall indicate that vehicular traffic may pass the signals and proceed straight on or to the left or to the right;
(d) the amber signal (when provided) shall, when shown alone, convey the prohibition that vehicular traffic shall not proceed beyond the stop line or, if there is no stop line, beyond the signals, except in the case of any vehicle which when the signal first appears is so close to the said line or signals that it cannot safely be stopped before passing the line or signals.
