D6.4.2 During contra-flow, i.e. when one carriageway of a dual carriageway road is to be operated temporarily to carry two-way traffic, the opposing traffic streams should be physically separated by means of a buffer zone or lane. Buffer zones are usually delineated by a line of cylinders with a line of temporary road studs either side as shown in Details H and K, see Table A1.5 (Appendix 1). Alternatively, separation may be effected using a temporary vertical restraint safety barrier. Advice on the use of temporary vertical restraint safety barriers is given in Section D3.10 and in TD 19 "Requirement for road restraint systems" (DMRB 2.2.8).
D6.4.3 Contra-flow sections of road should be subject to a mandatory speed limit (normally 50mph). Advice on the use of temporary speed limits is given in Section D3.7.
D6.4.4 In contra-flow situations it is essential that there is a continuous, well-defined and unobstructed route through the site which is available for use at all times by emergency vehicles, see Section D6.7.
D6.4.5 The signing arrangements required to operate two-way traffic on dual carriageway roads are illustrated in Sections D6.17 to 6.19.
D6.4.6 Signs to diagram 7210 to 7214 are used to show the diversion of one or more lanes from the primary carriageway on to the secondary carriageway. Each sign may have upper or lower panels added to describe particular characteristics, see paragraphs D4.10.14 and D4.10.15.
D6.4.7 Signs to diagram 7215 to 7220 are used to show the diversion from the secondary carriageway back on to the primary carriageway. Each sign may have upper or lower panels added to describe particular characteristics, see paragraphs D4.10.14 and D4.10.15.
D6.4.8 The need for signing, lighting and temporary barriers for pedestrians should be assessed where a contra-flow is to be introduced on an all-purpose dual carriageway road, particularly in an urban area; see Section D3.32.
D6.4.9 Designers should consider whether barriers should be used to restrict crossing points and whether additional signing is necessary to warn pedestrians of unusual or changed traffic movements, particularly in urban areas. If two-way working is to be introduced on a former one-way street then a "PEDESTRIANS LOOK BOTH WAYS" sign to diagram 7017 will be a minimum additional requirement. Carriageway markings will also need to be amended where appropriate and consideration should be given to the need for road markings to diagram 1029 "LOOK LEFT" or "LOOK RIGHT" to warn pedestrians that traffic may be approaching from an unexpected direction.
D6.4.10 The designer must take into consideration the effect of contra-flow working on signalled pedestrian and cycle crossings.
D6.4.11 Where it is necessary for traffic on one carriageway to be diverted on to the other carriageway, it is essential that the transition or temporary crossover is designed to an acceptable standard, see Section D6.5.
D6.4.12 Signs to diagrams 7230 to 7239, and prescribed variants, are used to show the diversion of individual lanes on one carriageway. Signs to diagrams 7230 to 7234 direct traffic to use the hard shoulder or rejoin the main carriageway. Signs to diagram 7234 direct one lane on to the hard shoulder with the other lane or lanes being directed to the right-hand side of the carriageway. Signs to diagram 7233 direct traffic to use the hard shoulder in order to leave at a junction ahead. Signs to diagrams 7235 and 7236 indicate the start and end of a section of narrow lane widths.
D6.4.13 Signs to diagrams 7237 to 7239 are used to show the diversion of lanes across the carriageway, without use of the hard shoulder. The sign to diagram 7240 is used to indicate access to a destination reached from a junction. Signs to diagrams 7250 and 7251 are used to indicate traffic lanes leaving and joining at a junction, whilst signs to diagram 7252 and 7253 are used to indicate traffic joining at a junction. Signs to diagram 7202 and 7255 are used to show the start and end of a lane closure.
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