Page:UK Traffic Signs Manual - Chapter 8 - Part 1 (Traffic Safety Measures and Signs for Road). Designs 2009.pdf/145

SINGLE CARRIAGEWAY ROADS

Where the junction is normally controlled by permanent signals, the position of the proposed works will dictate the most appropriate course of action. A temporary change in the position of the stop line and/or one signal head may suffice. Should the vehicle detectors for the permanent signals be located within the area of the works or if traffic is diverted so that the vehicle detectors cannot register the passage of vehicles, the traffic signal controller should be switched by the Highway Authority to provide a permanent demand on that phase. If the works are to continue for more than a few days and delays are likely due to fixed time operation, alternative detection arrangements should be considered. Where the capacity of an approach to the junction is reduced as a result of the removal of one or more lanes for an extended period, consideration should be given to adjusting the signal timings to minimise queue lengths on this approach.

Other situations may require the permanent signals to be switched off temporarily to allow traffic to be controlled either by a multiphase portable signal set or by one of the manual methods of control. When the permanent signal heads cease to be the operative signs, they must be covered.

Works in the vicinity of part-time signals, stand-alone crossings at roundabouts and full-time signal-controlled roundabouts can cause particular problems and the designer should contact the authority responsible before planning the necessary traffic management.

Whenever portable traffic signals are to be used to control traffic at road works involving a junction, e.g. as illustrated in Plan SC11 and Plan SC12, TSRGD require (direction 53) that the traffic authority’s written permission is obtained. The use of portable traffic signals is dealt with in Section D5.10.

Where the road works do not actually include a junction, but one is so close that difficulties may be encountered, the designer may consider that multiphase control of the junction and shuttle lane is inevitable, even though either the junction or shuttle lane taken in isolation would not require signal control. Local Transport Note 1/98, "The installation of traffic signals and associated equipment" includes the use of temporary traffic signals and says they should be to the same standard as permanent signals. This allows, for example, for pedestrian phases to be used. Portable signals cannot be used with pedestrian facilities at a junction.

Where the designer considers that a junction within a controlled area is of relatively minor importance and does not require to be separately signalled, consideration should be given to the provision of warning signs. Vehicles emerging from uncontrolled side roads will normally join the rear of the traffic stream proceeding in the direction in which they wish to go. However, if emerging vehicles do not have a clear view of both ends of the works, there is a danger that they will set off in one direction only to be confronted with a traffic stream proceeding in the other. For this reason it is essential that clear visibility is available from the side road to both ends of the works if it is not to be signalled separately.

The sign for traffic joining the controlled area from the side road is a sign with two arrows and the legend "TRAFFIC UNDER SIGNAL CONTROL" to diagram 7021 for use with a "road works" sign to diagram 7001. The sign to warn traffic proceeding through the controlled area is a sign with the legend "JOINING TRAFFIC NOT SIGNAL CONTROLLED" to diagram 7022 for use with an "Other danger" sign to diagram 562.

The "road works" sign to diagram 7001 and diagram 7021 should be sited not more than 10m in advance of the point at which traffic emerging from the junction would give way to passing traffic. The "other danger" sign to diagram 562 in combination with diagram 7022 should be located on each approach to the controlled area and should be positioned midway between the "traffic signals ahead" sign to diagram 543 and "road narrows" sign to diagram 517. The size of these signs should be in accordance with Table A1.2 (Appendix 1).

The "TRAFFIC UNDER SIGNAL CONTROL" sign to diagram 7021 must be erected in combination with the "road works" sign to diagram 7001 at every side road leading to an uncontrolled junction within a length of road controlled by portable traffic signals or "STOP/GO” boards. This procedure must be used only when traffic held at the signals is visible to the joining traffic. 144