20. The sign shown in diagram No. 209 may be placed only on or near a road if vehicular traffic complying with the sign would turn into a road, not being a one-way street, and the sign shown in diagram No. 210 shall be placed only on or near a road if vehicular traffic complying with the sign would turn into a road, being a one-way street.
21.—(1) Light signals ( other than such portable light signals as are referred to in Regulation 29 of the Regulations) for the control of vehicular traffic may be placed only at sites approved in writing by or on behalf of the Minister or the Secretary of State, as the case may be, after consideration of such plans for the sites, particulars of the apparatus to be used and information as to the volume and character of the traffic affected as he may require, provided that such approval in writing shall not be required to be obtained in respect of any installation to the cost of which the Minister or the Secretary of State has agreed to contribute either wholly or in part.
(2) Light signals ( other than as aforesaid ) may be used only in conjunction with a carriageway marking shown in diagram No. RMI in the Second Schedule to the Regulations and any lens of the size and colour shown in diagram 1 in the Third Schedule may only be fitted to such signals in any of the methods shown in diagrams Nos. 4 to 8 inclusive in that Schedule where vehicular traffic controlled by the signals is restricted by virtue of an Order, Regulation or Byelaw to proceeding in the direction indicated by the arrow shown in such lens or the directions indicated by the arrows where two such lens are fitted.
22. The sign shown in either of the diagrams Nos. 215 and 307 may be used only in combination with light signals prescribed by Regulation 27 of the Regulations and subject to the following provisions:
(a) the sign shall be so fixed that its lower edge is level with the bottom of the signal head;
(b) where the word "left" appears on the sign it shall be fitted on the left-hand side of the signals , and where the word "right" appears on the sign it shall be fitted on the right-hand side of the signals; and
(c) where there are any other light signals supplementary to the signals on which the sign is fixed , then a similar sign may be affixed to the supplementary signals in accordance with the foregoing provisions of this paragraph.
23. The sign shown in diagram No. 218 shall be used only by a person duly authorised by a highway authority for the purposes of section 27 of the Road Traffic Act, 1930, and may not be used during the hours of darkness as defined by the Road Transport Lighting Act, 1927.
24. Signs shown in diagrams Nos. 219 and 220 may be used only where one-way traffic working is necessary owing to a temporary closure to vehicular traffic of a width of the carriageway.
25. The sign shown in diagram No. 304 may be used only where the entry of vehicular traffic to a road is prohibited and only if two such signs are used one on each side of the road.
26. The sign shown in diagram No. 305 may be used only on a street refuge and as a supplement to a sign shown in diagram No. 304.
27. The sign shown in diagram No. 410 may be used only on or near a road on which there are more than two lanes for vehicular traffic.
