in advance, but should never be used if portable signals are in use at the same location. Where personnel are working on signals in close proximity to traffic, other than in short-term situations, the traffic signal maintenance sign (prescribed variant of diagram 7010.1) should be provided in advance of the signals.
D5.10.14 Sign variants to diagram 7014 include "SIGNAL TIMINGS CHANGED" and "SIGNAL PRIORITIES CHANGED AHEAD".
D5.10.15 The "HEAVY PLANT CROSSING" sign variant to diagram 511 is used at a haul route crossing; see Section D3.23.
PORTABLE TRAFFIC SIGNALS — PRINCIPLES FOR TWO AND THREE-LANE SINGLE CARRIAGEWAY ROADS
D5.10.16 These principles are illustrated in Plans SC7 and SC8.
The principles for advance signing are:
- a minimum of three advance signs are required:
- a "road works" sign (7001) on the near side only in both directions, in advance of the works; a distance plate (572) is required for roads with a permanent speed limit of 50mph or more,
- a "traffic signals ahead" sign (543) on the near side in both directions, in advance of the works;
- on a two-lane single carriageway road (Plan SC7): a "road narrows" sign (51 7) with supplementary plate "Singlefile traffic" (518) on the near side only in both directions. On roads with a permanent speed limit of 50 mph or more, "for" and a distance are required on the diagram 518 plate;
- on a three-lane single carriageway road (Plan SC8) marked as two lanes in one direction and one in the other: a sign (7206) on the near side of the two-lane approach to indicate that the centre lane is closed, with traffic on the off side of the works travelling in the opposite direction:
- for roads with a permanent speed limit of 40 mph or less, one sign (7206) is required,
- for roads with a permanent speed limit of 50 mph or more, one sign (7206) is required with a bottom panel (7208) indicating the distance to the works of 200 yards, placed 200m in advance of the works, and a second sign is required with a bottom panel (7208) indicating the distance to the works of 100 yards, placed 100m in advance of the works; and
- a "WHEN RED LIGHT SHOWS WAIT HERE" sign (7011) on the near side only in both directions, placed 15m in advance of the works. In some cases this distance may need to be increased to avoid a waiting vehicle blocking the path of vehicles as they leave the works.
The principles for the lead-in taper are:
- one "keep left/right" sign (610) is placed on the near side at the start of the taper,
- on a two-lane single carriageway road: coning to Detail B is used at an angle of 45° to the edge of the road,
- on a three-lane single carriageway road: coning to Detail B or C2 is used. Table 5.3 in Section D5.4 gives the taper length and the length of the guide island is dealt with in Section D5.11;
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