Page:UK Traffic Signs Manual - Chapter 8 - Part 1 (Traffic Safety Measures and Signs for Road). Designs 2009.pdf/168

 To minimise the need for personnel to cross the carriageway, consideration should be given to using permanently mounted remotely controlled signs in the central reservation. The main requirements for such signs are that they should be adequately protected from collision and should not need attention that requires a person to cross the carriageway.

Gantry signing can be used for advising road users of incidents and accidents and can also be used to provide advice about static and mobile temporary traffic management.

The newer generation of gantry signal systems being developed are capable of displaying a greater range of signs, with greater resilience to damage or failure and these may be used to display traffic management messages and signs.

These gantries may also be used to support temporary signs where this facility is included in the design. Careful planning, installation and removal are required to avoid damage to the gantry sign.

Most wide carriageways are equipped with MIDAS and MS3/MS4 motorway signals. The newer traffic control centre equipment now enables these variable message signs to display messages and symbols appropriate to the traffic management layout. When planning works on the wider carriageways, discussions should be held with the control centre to identify an appropriate MS3/MS4 signing plan.

For static road works signing, obscuration of the signs is considered to be the overriding problem with five or six lanes of traffic for drivers travelling in the centre lanes. Signs located on the hard shoulder and in the central reservation (if sufficient space is available) are likely to be obscured much of the time.

Overnight closure of the carriageway allows the works to be carried out quickly with little risk to the workers and minimal delays for drivers. In order to close the carriageway, it will be necessary to deploy temporary traffic management to first impose a 50 mph speed limit, and then to reduce the number of lanes to single-lane running before requiring the traffic to leave the motorway. To avoid problems with sign obscuration, the overhead gantries in advance of the closure will need to be used. At least two sets of matrix signs to diagram 6002 (move to the next lane) per lane being closed should be used, followed by a light signal to diagram 6031.1 (red cross prohibition signal) on the following two gantries before the start of the static traffic management closure, see Section D6.20.

Before this option is chosen, the suitability of the diversion route will need to be assessed along with the increased level of accident risk imposed on the alternative route. Reference should be made to Section D3.15 for advice on diversion routes.

For works close to the start of a wider carriageway section, any lane closures required should be installed upstream of the wider carriageway section, in the section of motorway that has no more than four lanes. This will allow standard temporary traffic management signing to be used to sign the lane closures.

On carriageways with five lanes, where the above is not feasible, and the works require closure of the near side lane, the following ’near side only lane closure and signing’ technique should be considered. The principles are based on those given in Plans DZB6, DZB7 and DZB8 but in this case the wicket signs (diagram 7202) in the central reservation are omitted. This technique should only be considered where the traffic volume on the lane to be closed, together with the volume of traffic on the two lanes adjacent to the closed lane through the works, does not exceed 2,400 vehicles per hour. This technique can also be applied on carriageways with six lanes where the works require closure of the near side two lanes.

Where neither D6.13.10 nor D6.13.11 applies, the initial closure should constitute the outside lane on a five-lane carriageway or the outside two lanes on a six-lane carriageway. Setting out signs and cones for this closure may require the use of the mobile lane or carriageway closure techniques and these are covered in Sections D6.26 and D6.27. Additional signing can then be implemented in the closed lanes using the standard signs without obscuration and sign size being a problem. 167