|Railways in the Southampton area|
Southampton Civic Centre Tunnel is a railway tunnel beneath the Civic Centre in the centre of the Hampshire city of Southampton, in England. Opening in August 1847, its construction linked the stations of Southampton Terminus and Southampton West End (later moved and now known as Southampton Central). The construction of the Southampton and Dorchester Railway linked London through Southampton to towns further west, such as Poole and Dorchester. The through link also accelerated the expansion of Bournemouth.
Construction and operating problems
Geological problems plagued the construction and delayed its opening. The fundamental issue was that the ground was already compromised by the partial construction of the Salisbury and Southampton Canal tunnel, which the railway tunnel crosses at an acute angle and slightly higher. Because the canal tunnel was lined with clay "puddle" it collects water which ends up in the rail tunnel making the latter very wet. In the 1960s an access was cut into the canal tunnel in order to examine it, although this was later sealed behind a new segmental wall structure when, between 1983 and 1985, the tunnel underwent extensive engineering works  and the line through it was worked as a single line for long periods while remedial work was carried out. A narrow gauge railway was set up as part of these works.
Services using the tunnel
The tunnel is mostly used by trains on the South Western Main Line from London Waterloo to Bournemouth and Weymouth, on the Wessex Main Line from Portsmouth to Bristol, and for journeys on the local line from Portsmouth to Southampton. Additional journeys are made on the West Coastway Line from Southampton to London Victoria via Gatwick Airport, and on the Cross Country services from Bournemouth to various points in the north of England.
There is also extensive use for freight, most of which is containers to and from Southampton Container Terminal just to the west of Southampton Central.
During the period Sunday 27 December 2009 to Sunday 3 January 2010 the tunnel closed for the track to be lowered to achieve W10 (freight container) route clearance. Previously, Hi Cube Intermodal container traffic had to be carried on special low wagons with areas which could not be loaded, resulting in both traffic planning issues and lower train capacity. Additionally, all container trains were restricted to 20mph when passing through the tunnel because of the limited clearances at the top edges of the loaded containers. Since rebuilding no speed or loading restrictions apply to the tunnel and container trains can travel at up to the line speed of 40mph, the limit for the tunnel. The work meant containers could be transported by rail from the Port of Southampton across the country in a quicker, cheaper, greener and more practical way.