Page:UK Traffic Signs Manual - Chapter 8 - Part 1 (Traffic Safety Measures and Signs for Road). Designs 2009.pdf/41

DESIGN CRITERIA If emergency diversions are likely to be a rare occurrence, the cost of permanent symbolic signing along diversion routes may not be justified. In this case, temporary diversion signs to diagrams 2702 to 2707 will have to be placed along the route if it is too complex for the route number techniques described above to be used.

Where the works temporarily impose a lower height restriction (for example, a safety platform or falsework underneath a bridge soffit) warning of the restriction must be given by means of the headroom at hazard sign to diagram 530, which should be attached to the structure, and by another headroom at hazard sign to diagram 530 with a distance to hazard plate to diagram 572 or 573 in advance of a suitable diversion point before the hazard; details of signing at bridges and other structures is given in Chapter 4, Section 7.

Where the works temporarily impose a lower height restriction at a structure that is already signed by virtue of the permanent headroom being below 16’-6" (5.03 m), since drivers might not notice the reduced dimensions on the standard signing, consideration should also be given to providing an additional sign as shown. While works are in progress, the sign would be deemed to be prescribed under regulation 53(1)(e)(i).

At all sites where works are being carried out above public roads, vehicles and pedestrians must be protected adequately from falling objects by nets, platforms or other devices. Before any reduction in working height is effected, the Highway Authority must be consulted so that hauliers and bus operators can be advised of the changed circumstances. The Highway Authority may require a licence and an indemnity for devices etc. placed over the highway.

Bridge heights must be checked each time the road is resurfaced or reconstructed and signs erected or altered as necessary. Detailed guidance can be found in Chapter 4 (paragraphs 7.7 to 7.9).

Where the work involves a reduction in height clearance at a structure an "OVERHEIGHT VEHICLE DIVERT" sign, which is prescribed in the Regulations in Schedule 15, Part II, may be erected before the preceding junction. Amber lamps flash when this sign is activated by an overheight vehicle detector. The sign otherwise shows a blank face.

Signs to diagram 7220 and 7240 may be used to show destinations at junctions within road works on motorways and non-motorways respectively. Lower panels described in Section D4.10 may be added.

Signs to diagrams 7250 to 7254 are used to show the lane configuration at junction entries and exits. Countdown distances may be shown on a lower panel in accordance with diagram 7256.

Consideration should be given to closing any entry slip roads that occur within road works on dual carriageway roads (see Section D6.21), particularly for overnight relaxation works. If this is not practicable, the traffic management at the junction should be designed as closely as possible to the original junction layout. 40