Page:UK Traffic Signs Manual - Chapter 8 - Part 1 (Traffic Safety Measures and Signs for Road). Designs 2009.pdf/35

DESIGN CRITERIA Where the footway is diverted into the carriageway it will be necessary to provide a safety zone between the outer pedestrian barrier and the live traffic. Where works are adjacent to or in the carriageway, a safety zone will need to be provided as described in Section D32. The outer edge of the safety zone will be delineated by traffic cones or cylinders. The inner boundary of the safety zone may be delineated by a lightweight barrier.

Traffic barriers for guiding vehicles past obstructions should be placed on the traffic side of the obstruction and should be red and white to diagram 7105, or where a driver is required to alter direction sharply to diagram 7104 and must be reflectorised (or illuminated internally or externally during the hours of darkness). Examples of the use of both types of barrier are shown in the plans in Section D5 and D6.

In some cases, it may be appropriate to provide a temporary vehicle safety restraint barrier acting as a traffic barrier. It may be appropriate to provide traffic barriers in addition or to mark the vehicle safety restraint barrier in accordance with diagram 7105.

Lightweight barriers may be used where there is no risk of pedestrians encountering the works or where there is a need to delineate the inner boundary of a safety zone.

Temporary vehicle restraint safety barriers compliant with BS EN 1317 may take the form of permanent type vehicle restraint safety barriers erected temporarily or purpose made temporary safety barriers. For further guidance on the use of vehicle restraint safety barriers refer to TD 19 "Requirement for road restraint systems" (DMRB 2.2.8).

Where it is evident at the design stage that a temporary vehicle restraint safety barrier will be necessary to protect road users and/or the workforce, its use should be specified as part of the design. The type and length that is needed will need to be based on the requirements and guidance given in TD 19. Other factors that should be considered are the time taken and means of installation, maintenance and removal of the safety barrier, implications arising from its use on works accesses and exits, the emergency services, wide loads, the duration of the works and the provision of a vehicle recovery service. Designers also need to take into account speed limits and the degree of deflection of the safety barrier which may occur in the event of an impact. In determining whether to include temporary safety barriers, the project designer shall undertake a risk assessment of the situation, considering the above factors, the cost benefit of the proposed use and any special arrangements which may be necessary to facilitate safe installation and removal.

Where a temporary vehicle restraint safety barrier is provided, the temporary road markings or studs used adjacent to the barrier should be to Detail E, F, or H as specified in Table A1.5 (Appendix 1).

Road markings are used at road works principally to delineate the carriageway edge or to divide the carriageway into traffic lanes. When during the course of road works operations, the road remains in use and dangerous conditions are likely to occur through the absence of road markings, temporary markings should be provided. Refer to Part 2: Operations, Section O4.12 for details relating to advice on the standards for temporary road marking materials and on the use of the "NO ROAD MARKINGS" advance warning signs to diagram 7012. 34