D6DUAL CARRIAGEWAY ROADS
D6.1GENERAL ISSUES
D6.1.1 This section deals with temporary traffic management design on dual carriageway roads, including motorways, both with and without hard shoulders.
D6.1.2 In order to determine the most appropriate temporary traffic management arrangement, a detailed survey of the highway is required. Precise carriageway widths, edge and drainage conditions and the presence and strength of any hardening of the central reservation will need to be determined.
D6.1.3 The designer should also review the traffic characteristics of the site. Traffic counts should be taken in each direction to record maximum flows. Seasonal variations may need to be taken into account. High proportions of commercial vehicles may preclude some layout designs where only one lane in each direction is allocated to vehicles wider than 6’-6" (2.0 m) (wider vehicles). Where cycle lanes are affected by road works the safety of cyclists will need to be considered.
D6.2HARD SHOULDER USE
D6.2.1 Where road works may seriously reduce the carriageway capacity, consideration should always be given to using the hard shoulder as a temporary running lane in order to maintain capacity and to avoid undue delay. The designer needs to ensure that this is acceptable to the Highway Authority and is discussed with the emergency services.
D6.2.2 A temporary traffic regulation order will be required in order to use the hard shoulder as a running lane. For further information on temporary traffic regulation orders, see Section D3.39.
D6.2.3 Provided that the hard shoulder is continuous, has adequate headroom and is strong enough to carry the expected traffic load, it should always be brought into use as a running lane if the expected traffic demand is likely to exceed the capacity of the normal traffic lanes left open. Thus the hard shoulder, when suitable, should be brought into use when the centre and right-hand lanes of a dual three-lane carriageway road are taken out of use or when the right-hand lane of a dual two-lane carriageway road is taken out of use, unless the traffic is expected to be light or the duration of the work short.
D6.2.4 Hard shoulders are sometimes of limited width, so the Highway Authority or the agent acting on its behalf must be consulted on the suitability of any length for use as a running lane. Emergency telephones and permanent signs may be situated close to the back of the hard shoulder, so the available clearance should be checked. The temporary removal of emergency telephones and permanent signs and the installation of new or additional vehicle restraint safety barrier may be necessary.
D6.2.5 Where hard shoulders are to be used as temporary running lanes carrying heavy traffic during maintenance works, they must be structurally adequate to carry the traffic for the period of such use and have a surface with skidding resistance similar to that of the permanent running lanes.
D6.2.6 Assessment of the surface condition of the hard shoulder and the need for remedial works are integral parts of the planning of all major maintenance works. These need to be undertaken well in advance to ensure that the investigations are adequate and that remedial works are effected without prejudicing the works programme. Advance treatment of the hard shoulder surface might not always be possible and it will then be necessary to rely on warning signs.
D6.2.7 Any adverse camber likely to cause driving problems should be eliminated if possible or otherwise suitable warning signs must be erected to warn drivers.
D6.2.8 Where there are chambers, manholes or other features within the hard shoulder the designer should ensure that these will adequately support the running lane traffic for the duration of the works. Where
153
