(2) As exceptions to the provisions of the preceding sub-paragraph, the signs shown—
(a) in diagram 606 when erected on the central island of a roundabout or when used in combination with a plate of the type shown in diagram 608.
(b) in diagram 609 when used in the said combination or when placed on a road approaching its junction with a dual-carriageway road,
(c) in diagrams 616, 1046 and 1047 when placed at a site which has been approved in writing by or on behalf of the Secretary of State, and
(d) in diagrams 712.1, 7193A and 729.2 when including a symbol represented in any of the diagrams in Part I, and no symbol so represented in Part II of Schedule I to the Regulations,
may be placed on or near a road in the circumstances prescribed respectively at (a) to (d) above for those signs notwithstanding that they do not in those circumstances so indicate as aforesaid.
In this paragraph "dual carriageway road" means a length of road on which one part or the carriageway is separated from another part by a central reservation, and "central reservation" means works, not consisting in a street refuge, provided in a road for separating one part of the carriageway of that road from another part for the safety or guidance of Vehicular traffic using that road.
7. The signs shown in diagrams 701 to 717 may be placed only on or near a primary route and the signs shown in diagrams 711 to 726 may be placed only on or near a non-primary route, except that the signs shown in diagrams 713.2 and 713.3 may be placed on or near any road when varied to include a blue border.
8. The signs shown in diagrams 823 to 825 when the colour of the background is blue may be placed only on or near a motorway, when the colour of the background is green may be placed only on or near a primary route and when the colour of the background is white may be placed only on or near a non-primary route; and the signs shown in diagrams 837.1 in 838.2 may be placed only on or near a primary route or a motorway.
9. The sign shown in diagrams 901.1 in 925 may he placed only on or near a motorway.
10. The traffic Signs shown in the diagrams whose numbers appear in column 1 of the table set out in this paragraph shall not be used on a road unless so used in conjunction with the road markings shown in the diagrams whose numbers appear in column 2 of that table opposite to the number in column 1 to which they relate;
Provided that the provisions of this paragraph requiring the use or the signs shown in diagrams 601.1, 602, 611.1 and 650 in conjunction with a road marking shall not apply during the execution of works on a road in the vicinity of the place where any of those signs is erected, if those works necessitate the temporary removal of that marking, and shall not apply if any or those signs is erected only temporarily in connection with the execution of works on a road.
