Page:UK Traffic Signs Manual - Chapter 8 - Part 2- Traffic Safety Measures and Signs for Road Works and Temporary Situations) - Operations 2009.pdf/57

 traffic delineators to diagram 7102, and cylinders to diagram 7103 are prescribed traffic signs. Traffic cones and cylinders should conform to BS EN13422:2004 "Portable road traffic signs – Cones and cylinders" and must comply with regulation 56; see also Part 1: Design, Section D4.9.

Oil drums, barrels or other containers shall not be used to delineate road works.

Cones should be placed close enough together to give an impression of continuity and an appearance of substance. The size of cone and the rate of taper to be used on different classes of road are specified in the Table A1.3 (Appendix 1), which also gives details of the cone spacing depending on their location in a layout and the type of works involved.

For works of short length a minimum of two cones should be placed between the entry and exit tapers. In adverse weather conditions, especially fog, cone spacings may need to be reduced in order to continue to give drivers adequate guidance past the obstruction. On roads subject to the national speed limit, 9 m spacing should always be the maximum in these conditions. Special arrangements for cones at builders’ skips are described in Section O3.29.

Flat traffic delineators to diagram 7102 are blades which are fixed to heavy bases. They have the same elevation as conventional traffic cones and may be used as an alternative on dual carriageway roads. BS 8442 includes a specification for flat traffic delineators.

The edge of carriageway road marking which is normally placed on the road surface 500 mm from the centre line of the cones may be placed on the edge of the base of a flat traffic delineator provided that:
 * when placed on the road their bases touch and their traffic face edges provide a continuous smooth line (bases which have white lines incorporated on them, but are used in other circumstances, should be oriented so that the white line is at the back so that it is less visible to drivers of approaching vehicles);
 * the white line comprises a white reflective strip 100 mm wide firmly adhered to the base;
 * the edge of the base where the white line is to be attached comprises a sloping surface, which is at an angle to the road surface of no more than 60° and is of such dimensions either to accommodate the 100 mm wide white line fully, or, where the angle between the road surface and the sloping surface exceeds 30°, to accommodate at least 80 mm of the width of the white line, the excess (max 20 mm) being returned on to the top surface of the base; and
 * the material from which the base is made allows proper adhesion of the white reflective strip.

When flat traffic delineators are placed so that the retroreflective surfaces are at right angles to the approaching traffic they can offer benefits of improved visibility during hours of darkness over conventional traffic cones. Unlike conventional traffic cones, however, flat traffic delineators are only visible for limited traffic approach angles (the angle between the normal to the sign face and the direction of the approaching traffic). It is therefore recommended that the following conditions are met whenever they are placed at road works: 55
 * flat traffic delineators should be used only where they may be placed with the white retroreflective surface facing the approaching traffic, so that the angle between the sign face and the direction of approaching traffic is as close to 90° as possible, but under no circumstances less than 50°;
 * flat traffic delineators should not be used within 50 m of "at grade" entry junctions on allpurpose dual carriageway trunk roads; and
 * flat traffic delineators should be stored separately from ordinary traffic cones to prevent accidental use on single carriageway roads.