17. The signs shown in diagrams 564 to 569 and 829 may be placed on or near a road only in connection with the execution of works thereon or a temporary obstruction thereon and any such sign so placed and any other sign shown in a diagram in Schedule 1 to the Regulations placed on or near a road in either connection as aforesaid shall not be retained on or near the road after the completion of the works or the removal of the obstruction, as the case may be.
18.—(1) Signs shown in diagrams 603 and 604 may be used only where one-way working is necessary owing to a temporary closure to vehicular traffic of a width of the carriageway of a road.
(2) The signs shown in diagrams 615 and 811 may only be used in conjunction with one another and shall not be used in conjunction with the signs shown in diagrams 603 or 604.
19. The sign shown in diagram 605 shall be used only by a person duly authorised by a highway authority for the purposes of section 224 of the Road Traffic Act 1960 (which relates to the weighing of motor vehicles) and may not be used during the hours of darkness.
20. Signs shown in diagrams 830 to 832 may be used only—
(a) in connection with a traffic census the taking of which on a road has been approved by the highway authority for that road, by the chief officer of police of the police area in which the road is situate, and by or on behalf of the Minister or the Secretary of State, as the case may be; and
(b) in the vicinity of the traffic census points appointed by or on behalf of the Minister, or the Secretary of State, as the case may be.
21. The signs shown in diagrams 833 to 836 may be used only to regulate the movement of vehicular traffic into and out of premises with more than one access to a road.
22. The sign shown in diagram 536 shall be mounted on two posts and so much of each post as extends above ground level shall be coloured black and white in alternate horizontal bands, each band being not less than 11 inches nor more than 13 inches in depth.
23.—(1) The sign shown in diagram 560 or diagram 561 shall be so placed that the top of the sign is not less than 2 feet 6 inches nor more than 4 feet 6 inches above the surface of the carriageway in the immediate vicinity.
(2) Where the sign shown in diagram 560 or diagram 561 is mounted on a post specially provided for the purpose, that part of the post which extends aboveground level shall be coloured black and white in alternate horizontal bands, each band being not less than 9 inches nor more than 13 inches in depth.
24. The road marking shown in diagram 1001 may be placed on a road only in conjunction with the light signals prescribed by Regulation 31 or those light signals as varied in accordance with Regulation 32 of the Regulations or at a site where vehicular traffic is from time to time controlled by the police.
25. The road markings shown in diagrams 1002 and 1022 may be placed on a road only in conjunction with the sign shown in diagram 601.
26.—(1) The road marking shown in diagram 1017 may be placed on a side of a road only for the purpose of indicating a statutory prohibition or restriction on the waiting of vehicles (but excluding waiting for the purpose of loading or unloading a vehicle) which applies on that side for at least eight hours during the period from 7 a.m. to 7 p.m. on at least four days other than a Sunday in any week.
