To ask the Secretary of State for Transport (1) how many vehicles on the M6 use the Thelwall viaduct each day; (2) what plans his Department has made to ensure that the Thelwall viaduct is opened as soon as possible; and if he will make a statement; (3) what plans he has for re-routing traffic in the north-west in order to minimise the disruption caused by the closing of the Thelwall vaiduct; (4) what assessment he has made of the economic impact on local business of the closing of the Thelwall viaduct; (5) what estimate his Department has made of how long it will take to repair the Thelwall viaduct; and if he will make a statement; (6) what research his Departments has
(a) commissioned and (b) evaluated on the longevity of the Thelwall viaduct after the repairs; and whether there are plans to avoid similar problems in the future. 
I have asked the Chief Executive of the Highways Agency, Tim Matthews, to write to my hon. Frien.
Letter from Tim Matthews to Mr. Woodward, dated 14 April 2003
I have been asked by David Jamieson to reply to your six recent Parliamentary Questions about ongoing works to the northbound bridge of the M6 Motorway Thelwall Viaduct, in Cheshire.
The Highways Agency is responsible for the operation, management, maintenance, and improvement of the trunk road and motorway network in England, including the Thelwall Viaduct, which typically carries some 150,000–160,000 vehicles per day. All but one lane of the northbound viaduct was closed in July 2002, following the discovery of a failed roller bearing.
Detailed investigation has concluded that all 136 roller bearings on the northbound viaduct should be replaced before further traffic lanes can be opened on the viaduct. The increased scale of the problem has led to a thorough analysis of all the issues on the viaduct and, over the course of the next few months, this further work will enable us to establish a realistic programme for the works.
The current restrictions comprise three narrow lanes in each direction on the new southbound viaduct and a single lane on the northbound viaduct, to facilitate traffic leaving the M6 at Junction 21, in Warrington. There are advance warning signs on all the Motorway approaches to the works advising of likely delays, but there is no convenient diversion route using the motorway network. Traffic could be diverted along the M62, M60, M56, and A556, but this would add around 15 miles to journey lengths, and parts of this diversion are already at full capacity during peak periods. We will continue to monitor traffic patterns closely and keep under review all possible diversion routes to mitigate the effect of the restrictions.
Laboratory testing and investigations into how the bearings have failed is substantially complete. These findings will be used to inform the design process for the replacement of the bearings and associated works required to bring the structure back fully into long-term service. A different kind of bearing has been specified to replace the failed roller bearings. We are content that these bearings will not be susceptible to the same failure as the existing bearings, and that there is no risk of a repetition of the problem. Our thorough maintenance inspection regime revealed the current problems and this regime will continue to monitor the condition of this and our other bridges in future years.
We are conscious of the effects that restrictions on the viaduct are having on local businesses, and are working closely with affected stakeholders, in particular Warrington Borough Council, to identify the scale of the impact on the local community. Traffic-count information on both motorways and the local road network is being collected to enable the changes in driving patterns to be quantified and appropriate mitigation measures devised.
We are currently looking at a phased re-opening of lanes on the northbound viaduct. Initially, the strategy will be to open a second lane on the northbound viaduct at the earliest opportunity. This will enable four running lanes to be reinstated in each direction and should significantly reduce delays for southbound traffic, which is currently restricted to three lanes.
I hope this is helpful. If you would like any further information about this matter, you may wish to contact the Agency's Project Manager for the viaduct repairs, Paul Hupton, Room 703, Sunley Tower, Piccadilly Plaza, Manchester, M14BE (Tel 0161 930 5641).