Page:UK Traffic Signs Manual - Chapter 8 - Part 1 (Traffic Safety Measures and Signs for Road). Designs 2009.pdf/34

 In adverse weather conditions, especially fog, traffic cone spacings may need to be reduced in order to continue to give drivers adequate guidance past the obstruction. 9 m spacing should always be the maximum in these conditions.

For works on motorways and all-purpose dual carriageway roads with hard shoulders, where there are long straight runs and there is good visibility, the 9 m longitudinal spacing of traffic cones may be relaxed to 18 m. In this case the spacing of the warning lights should also be 18 m, see Table A1.3 (Appendix 1).

For works of short length a minimum of two traffic cones should be placed between the entry and exit tapers.

Special arrangements for traffic cones at builders’ skips are described in Part 2: Operations, Section O3.29.

Traffic cylinders can be fixed into the bases of existing depressible road studs or into purpose-made bases. They are used to separate opposing flows of traffic where one carriageway of a dual carriageway road is required to carry two-way traffic or to separate two lanes which are to become segregated or to be rejoined.

Obstructions and excavations should be adequately guarded at all times. Barriers may be used to protect all persons from roadside hazards, obstructions/excavations and/or for the protection of the workforce from an errant vehicle.

Barriers should be visible by day and night. Barriers, other than vehicle restraint barriers, adjacent to running traffic lanes should be guarded by a line of traffic cones, augmented by warning lights at night. Barriers may also constitute a traffic sign, see paragraph D3.10.7 below.

There are four basic types of safety barrier that may be used: 0 pedestrian barriers;


 * traffic barriers for guiding vehicles and indicating that a traffic lane or part of a traffic lane is closed,
 * lightweight barriers for delineating the inner edge of safety zones, and
 * vehicle restraint safety barriers.

Requirements for maintaining pedestrian mobility are set out in Section D3.32. Particular attention should be paid to the needs of people with mobility and visual impairments. A pedestrian barrier should be provided on those sides of an obstruction that restrict pedestrian flow or are accessible to pedestrians.

Pedestrian barriers alongside excavations should be the subject of a risk based assessment. Barriers alongside excavations greater than 300 mm in depth in high duty areas (>22 persons per minute, per linear metre width, for at least half of the working day) should be able to withstand crowd pressure and be at least 300 mm clear of the edge of the excavation. These barriers should comply with BS 7818 "Specification for pedestrian systems in metal". Lesser pedestrian trafficked footways may use other approved barrier systems that are rigid enough to guard pedestrians from traffic, excavations, plant and materials and withstand wind pressures. 33