Page:UK Traffic Signs Manual - Chapter 8 - Part 1 (Traffic Safety Measures and Signs for Road). Designs 2009.pdf/70

 *road closures and prohibited turns;
 * bus, cycle and taxi lane closures;
 * clearways/waiting restrictions;
 * width/height restrictions;
 * weight restrictions and arrangements to deal with overweight vehicles;
 * wording of orders to ensure they reflect pattern and phasing of works; and
 * arrangements for escorted vehicles.

The designer should anticipate the effect of the works on the flow of traffic and endeavour to minimise delays whilst being careful not to compromise safety. Advance road user and frontager notification and advance signing are the first steps in addressing this problem by seeking to remove a proportion of the flow from the route. Early publicity will allow some road users to plan their journeys to avoid the congestion caused by the works and frontagers to take appropriate action.

When appropriate, publicity should also cover the impact on bus routes and bus stops and should be carried out in conjunction with the relevant bus operators. To meet the needs of passengers with mobility and visual impairments, the use of different types of media including websites and local radio should also be considered.

This section deals with tunnels, although underbridge and underpass structures will have certain features in common with tunnels, e.g. lighting, fire safety, access and escape provisions and may also include ventilation and lane control provisions, so many of the design comments relating to traffic management in tunnels may apply equally to these types of highway structures.

Tunnels should be designed in accordance with the guidance given in BD 78 "Design of Road Tunnels" (DMRB 2.2.9), or other equivalent standards, which covers enclosed road tunnels of 150m or more in length. The document provides information on the general considerations and specific design and operational requirements of road tunnels, including the provision of carriageway crossovers and temporary contra-flow traffic management. The temporary traffic management proposals for new and existing tunnels should be in accordance with the principles set out in this Chapter.

For ventilation and fire safety reasons most new road tunnels, and particularly those on the motorway and trunk road network, comprise two separate bores, with each bore accommodating a carriageway carrying unidirectional traffic during periods of normal operation. It is normal procedure to close a bore of a twin bore tunnel to facilitate planned maintenance, unless it has been designed to support partial closure and the safety zone minimum safety clearances given in Section D3.2 can be maintained.

The following considerations also apply to tunnels that operate a bi-directional traffic flow, or for a single bore, where it is proposed to run traffic in the opposite direction to its normal lane/carriageway traffic flow. 69