Page:UK Traffic Signs Manual - Chapter 8 - Part 1 (Traffic Safety Measures and Signs for Road). Designs 2009.pdf/269

CONVOY WORKING

Positive traffic control should be provided by means of manually operated portable traffic signals or manually operated "STOP/GO" boards on single or dual carriageway roads, and at side road junctions with dual carriageway roads, with manually operated "STOP/GO” boards only. During the hours of darkness each sign face must be adequately illuminated by its own source of lighting; see paragraph D4.7.1. These methods of control are as described in Section D5.10 (portable traffic signals) and Section D5.8 ("STOP/GO” boards).

On single carriageway roads the length of site subject to traffic control should normally be restricted to a maximum length of 300m for portable traffic signals and 500m for manually operated "STOP/GO" boards, these being the maximum permitted lengths; see Section D5.8.

On dual carriageway roads the length of site subject to traffic control by portable traffic signals or manually operated "STOP/GO" boards should be restricted to a maximum of 1500m.

On high-speed single carriageway roads and dual carriageway roads, two signal heads should be used, one on the near side verge and one on the off side verge. On other roads a single head should be used, positioned to optimise its visibility to approaching traffic. In most cases a position to the centre of the carriageway behind the traffic management coning at each end of the works will be satisfactory.

It is important that the arrangements for imposition of mandatory limits are discussed and agreed with the police.

A temporary mandatory 10 mph limit must be imposed throughout the length of the works which is subject to convoy working. This should extend a short distance beyond the works so that the tail of the convoy is held to 10mph or less until it has passed the works. Generally an extension of the coned section will be necessary to prevent overtaking of the convoy vehicle.

Consideration should be given to making the speed limit variable so that a 30 or 40mph restriction comes into force when the appropriate signs are displayed, i.e. 30 (or 40) mph for use when the convoy vehicles have been withdrawn. If the permanent limit is 30mph, the existing "30" terminal signs (and "30" repeaters if this was an unlit road subject to a 30 mph limit) would be uncovered. Where the permanent speed limit exceeds 30mph, a temporary 40mph limit would be imposed and new terminal and repeater signs would have to be provided. Any existing speed limit signs must be completely covered or removed.

On all high-speed roads, a temporary mandatory limit of 20mph below the permanent limit prevailing on the road should be imposed in advance of the temporary 10mph limit; see Section D3.7.

Repeater temporary speed limit signs must be provided, these should be sited at the intervals indicated in Plans CW1 and CW2. On dual carriageway roads a 750 mm diameter repeater sign should be used and 600mm diameter on single carriageway roads.

Where a side road joins a section of a road subject to convoy working, a 10mph speed limit sign must be provided on each side of the side road, and any conflicting signs covered or removed.

Provision needs to be made for whenever convoy working is required to be withdrawn. The 10mph signs must be covered or removed until such time as they are required to be reinstated. Checks should be made between changes of speed limit that there are no conflicting signs, this is particularly important after the last change at the completion of the working day. 268