ROUNDABOUTS ON DUAL CARRIAGEWAYS
5.13 A plain bollard should be used on the central reservation of a dual carriageway or on the splitter island of any other road leaving a roundabout. A bollard may be dispensed with where a directly-lit direction sign is provided in such a position. If the physical layout does not adequately deter traffic from turning into the wrong carriageway or slip road in such situations, direction 7(3) permits "no entry" signs to diagram 616 accompanied by NO ENTRY markings on the carriageway (diagram 1046) to be used without the need for a traffic order, subject to the prior approval of the Secretary of State (see para 1.2). Further guidance on the signing of roundabouts may be found in paras 2.13 to 2.19, 3.13, 3.19 to 3.23 and 5.7.
GAP CLOSURES
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A distance in yards to the nearest ten yards may be added before or substituted for "AHEAD"
5.14 Where a gap in the central reservation of a dual carriageway has been closed, a temporary sign to diagram 7014 (see para 1.17 for guidance on size) varied to "GAP CLOSED AHEAD" should be provided, warning drivers of the changed layout. This should be sited on the central reservation a suitable distance in advance of the closure. It will usually be helpful to add the distance in yards (to the nearest 10 yards) on a separate line after "CLOSED". "AHEAD" may then be omitted. This sign must not be retained for longer than three months (direction 37). A "no right turn" sign (diagram 612) should be placed on the central reservation immediately preceding the former gap. Although not time-limited by direction 37, this should be removed at the same time as the GAP CLOSED sign. Junction warning signs may need to be removed or replaced (e.g. diagram 506.1 indicating a side road might have to be substituted for diagram 504.1 indicating a crossroads). Amended side road signing should be in accordance with para 5.15.
SIDE ROADS
5.15 Where a minor road crosses or joins a dual carriageway, GIVE WAY or STOP signs (see Chapter 3) should normally be provided on the minor road, supplemented by a "Dual carriageway" plate to diagram 608 (see para 2.1). Where advance warning is needed, signs to diagram 501 supplemented by the plates 502 or 503 as appropriate should be erected in accordance with table 2-1. The "Dual carriageway" plate may be provided below these signs also.
5.16 Special care is needed in signing minor road junctions with dual carriageway roads if the carriageways are separated by a very wide central reservation and the further carriageway could be mistaken for a separate road or cannot easily be seen by a driver on the minor road. In such cases, as an additional safeguard, NO ENTRY (diagram 1046) should be marked on the nearer carriageway to prevent drivers from turning right into it. It may also be appropriate to erect "no entry" signs (diagram 616) on each side of the nearer carriageway, angled so as to be seen by a driver attempting a right turn. Prior approval must be obtained in writing from the Secretary of State before using these signs and markings in such circumstances (see para 5.13). If the layout is not self-evident, a map-type sign on the minor road approach might be helpful.
5.17 On a side road which joins a dual carriageway road where there is no gap in the central reservation, a "turn left ahead" sign (diagram 609) together with a "Dual carriageway" plate (diagram 608) should be used. A "turn left" sign (diagram 606) with a "Dual carriageway" plate should be erected on the central reservation opposite the side road (see figure 5-1).
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