Southampton Tunnel is a railway tunnel that runs beneath the Civic Centre in the centre of the Hampshire city of Southampton, in England. The tunnel was constructed by the Southampton and Dorchester Railway to connect together the stations of Southampton Terminus and Southampton West End, which was subsequently relocated and presently known as Southampton Central. Directed by the experienced civil engineer Samuel Morton Peto, the majority of the tunnel was constructed using traditional cut-and-cover techniques. Its route mirrored that of the Salisbury and Southampton Canal, an incomplete project that had partially built an earlier tunnel; the presence of this earlier engineering work would negatively impact the project, causing damp and a partial collapse during construction. The opening of Southampton Tunnel had to be delayed until two months after that of the rest of the line, being finally opened to traffic for the first time during August 1847. Carrying a pair of tracks throughout its length, it has been periodically operated as a single-track tunnel only while periodic remedial work was performed. Southampton Tunnel has been used by a variety of direct passenger services connecting as far as London. In addition, the tunnel has facilitated large amounts of freight movements to and from the Southampton Container Terminal. During the 2010s, it was subject to extensive reengineering works, successfully raising both its loading gauge and maximum speed.
Construction
During 1845, approval for the construction of a railway to serve Southampton, Ringwood, Poole and Dorchester was secured from Parliament. The Southampton and Dorchester Railway's line was to run from Northam Junction and through the town centre along the surface to a planned station adjacent to Royal Pier. According to local historian Jake Simpkin, for the proposed railway to traverse the hill at Marlands, the construction of Southampton Tunnel was the only realistic choice, as a surface alignment would have severely impacted the planned development of parkland around Southampton. To oversee the tunnel's construction, the services of the experienced civil engineer Samuel Morton Peto were commissioned. Experienced miners from Cornwall were also recruited for the project, their specialist skills being valued. It was decided to construct the majority of the tunnel using the traditional cut-and-cover, only a limited section was actually bored out. The route selected for the tunnel mirrored that of the Salisbury and Southampton Canal, an earlier canal project that had been abandoned four decades earlier. However, the incomplete canal tunnel has compromised the ground considerably, and thus geological problems would plague the railway tunnel, both during its construction and operation. Due to the specific alignments of the two tunnels, the railway tunnel crossing canal tunnel from a slightly higher acute angle, combined with the canal tunnel's clay lining, water would continuously accumulate in the railway tunnel and make it very damp. Just prior to the tunnel's planning opening date, flooding around the area of the canal tunnel caused a partial collapse, forcing its opening to be delayed. While the railway itself would be opened in June 1847, Southampton Tunnel was only able to be opened to traffic two months later. While the tunnel alone was closed, passengers were conveyed to waiting trains at either side of the tunnel via specially-chartered buses.
Operating history and services
During the 1960s, an access passage was cut into the canal tunnel to allow engineers to survey its condition, although this interconnection was subsequently sealed behind a new segmental wall structure during the 1980s. For protracted periods, the line through Southampton Tunnel has been worked as a single line while rounds of remedial work have been carried out. Between 1983 and 1985, British Rail decided to perform extensive engineering works to facilitate the movement of larger containers through Southampton Tunnel. As part of these works, a narrow-gauge railway was operated. Presently, Southampton 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, the majority which is containers to and from Southampton Container Terminal just to the west of Southampton Central.
Between 27 December 2009 and 3 January 2010, the tunnel was temporarily closed while it underwent reengineering work. Specifically, the track was lowered to achieve W10route 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 20 mph when passing through the tunnel due to the limited clearances for 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 40 mph, the limit for the tunnel; accordingly, container trains could be more easily run to and from the Port of Southampton. Network Rail projected that the scheme would see 50,000 fewer lorries on the national road network due to the increased viability of freight services as a result of the wider scheme, which was reportedly costed at £71 million.
Film
Footage at the start of the film Oh, Mr Porter! features the tunnel at Southampton, filmed from the rear of the train and reversed for showing.
