D6.23MERGE IN TURN SIGNING
D6.23.1 This section provides guidance on the use of merge in turn signing which may be used to supplement lane closure signing at sites where a two-lane dual carriageway is being reduced to one lane, and regular and substantial queuing is likely to occur. It is likely to be particularly useful at sites where single-lane queues block back and affect secondary junctions.
D6.23.2 There is currently no evidence to indicate that merge in turn signing is suitable for three to one or three to two-lane closure situations and therefore such signing arrangements for carriageways with three or more lanes are not included in this document.
D6.23.3 Merge in turn is the process of two traffic flows combining into one by shared alternate priority.
D6.23.4 Merge in turn should only be considered when significant queuing is likely on the approach to lane closures at road works for substantial parts of the day. It should be noted, however, that the technique involves the deployment of a significant number of additional signs.
D6.23.5 The equal use of both lanes for queuing shortens the physical extent of the queues and so reduces delays arising from interference with upstream junctions.
D6.23.6 Merge in turn signing should be used only where there is a temporary mandatory speed limit of 50 mph or less imposed at the works site.
D6.23.7 Merge in turn is facilitated by using signs "WHEN QUEUING USE BOTH LANES" and "MERGE IN TURN" in addition to the standard temporary lane closure signing. Both signs should carry legends with an x-height of 125 mm (175 mm capital letter height), use white legend on a red background when used on all purpose roads, and black legend on a yellow background on motorways. The legend on each sign should be arranged to read as follows:
D6.23.8 The "WHEN QUEUING USE BOTH LANES" sign should be located on both sides of the carriageway and located 1000 m and 700 m in advance of the taper, and for longer queues at 500 m intervals to the furthest point upstream to which queues are likely to extend. The "MERGE IN TURN" sign should be deployed on both sides of the carriageway and located 300 m in advance of the taper. Plan DMT1 shows a simple merge in turn layout.
D6.23.9 Merge in turn signing does not require special sign authorisation because it is deemed to be prescribed by regulation 53(1)(e)(i) in TSRGD 2002. The use of the two merge in turn signs, described in paragraphs D6.23.7 and D6.23.8 above and illustrated in Plan DMT1, is recommended when merge in turn signing is being considered for works in England.
D6.23.10 The design of the merge in turn signs used in Wales and Scotland may differ from that specified in paragraphs D6.23.7 and D6.23.8. When the use of such signing is being considered in one of these countries, the appropriate Overseeing Organisation should be consulted.
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