Blackwall Tunnel

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Plaque at the northern entrance to the tunnel

The Blackwall Tunnel is a pair of road tunnels underneath the River Thames in east London, linking the London Borough of Tower Hamlets with the London Borough of Greenwich. The northern portal lies just south of the East India Dock Road (A13) in Blackwall; the southern entrances are just south of the Millennium Dome on the Greenwich Peninsula. Before the opening of the Dartford Tunnel in 1963, the Blackwall Tunnel was the easternmost river crossing for vehicles, excluding ferries.

The northern approach takes traffic from the A12 and the southern approach takes traffic from the A2, making the tunnel crossing a key link for both local and longer-distance traffic between the north and south sides of the river. It forms part of a key route into central London from south-east London and Kent. For some years, the section north of the A2 Rochester Way Relief Road was classified as a motorway (the A102(M)); however, this reverted to being the A102 in September 1999 when the part of A102 north of the river was merged with the newly opened extension of the A12 through Wanstead, Leytonstone and Leyton prompting a rationalisation of the area's road numbering systems.

[edit] History

The northern ventilation towers for the new Blackwall tunnel. (February 2006)

The older western tunnel was designed by Sir Alexander Binnie and built by S. Pearson & Sons, between 1892 and 1897. It was originally commissioned by the Metropolitan Board of Works but responsibility passed to the London County Council when the former body was abolished in 1889. The cost of the project was £1.4 million, and seven lives were lost during construction. The tunnel was officially opened by the Prince of Wales on 22 May 1897.

It was then the longest underwater tunnel in the world at 4,410 feet (1,344 m) long. It was constructed using tunnelling shield and compressed air techniques; the shield pioneer James Henry Greathead was a consultant. Sir Joseph Bazalgette, the architect of the London sewerage system, was also involved in the original planning of the project. To clear the site in Greenwich, more than 600 houses had to be demolished, including one reputedly once owned by Sir Walter Raleigh.

Today the western bore is only used for north-bound traffic (and is not accessible to vehicles taller than 4 m). The southern portal features a striking gateway built of red brick. The tunnel itself has several sharp bends. Some suggest these were built so that horses would not bolt once they saw daylight (motor vehicles were rare in 1897), though the bends may also have been created so that the tunnel avoided the foundations of other structures; another theory suggests the bends avoided tunnelling through a Black Death burial ground. The tunnel carries two lanes of traffic, though higher vehicles need to keep to the left-hand lane so that they do not hit the tunnel's inner lining.

The newer, eastern, tunnel, opened on 2 August 1967, is much wider, usable by vehicles up to 4.72 m and has no sharp corners — very much designed for 20th century road traffic. Its distinctive ventilation towers (right) were designed in 1961-2 by Terry Farrell when he was working as an architect for the London County Council. The northern pair stand at Blackwall, while the southern are now contained within the Millennium Dome. The towers were Grade II listed in 2000.

[edit] Traffic management

The Blackwall Tunnel is a notorious traffic bottleneck. Long tailbacks form in the morning rush hour on weekdays as traffic heads north from SE London and Kent towards central London. The transport authorities therefore try to increase flows by opening one lane of the eastern tunnel to northbound traffic for two hours; this, of course, means there is only one lane for southbound traffic so the northern approaches quickly become jammed each morning. Unfortunately, the western tunnel is not suitable to operate a similar two-way flow in the evening, so the northern approaches are frequently even more congested in the late afternoon and early evening.

Street maps of London periodically show a third Blackwall Tunnel as proposed for construction, though this does not appear in the latest edition of the London A-Z. Although congestion relief plans are regularly discussed, there are at present (2006) no specific plans for a third crossing at the site, although a 'reserved route' in an E-W direction does exist on the Greenwich Peninsula 'Master Plan'. If a new crossing were to be built, it would probably be a bridge towards Silvertown, rather than following the line of the existing tunnels, and all the crossings would be likely to become tolled.

The nearest alternative crossings are the Rotherhithe Tunnel three miles (5 km) to the west or the Woolwich Ferry two miles (3 km) to the east.

The tunnels do not allow pedestrians, but a bus route (London Buses route 108) operates through the tunnel. When the service is not running, the nearest pedestrian crossings of the river are the Woolwich foot tunnel adjacent to the Woolwich Ferry (see above - the ferry also carries pedestrians) and the Greenwich foot tunnel about two miles (3 km) to the west; the Rotherhithe Tunnel three miles (5 km) to the west does permit pedestrians, but walking through the tunnel is not advisable due to heavy exhaust emissions and poor ventilation. However, there is Jubilee Line tube service from North Greenwich tube station (TfL) to Canning Town station on the east and Canary Wharf tube station on the west, and the Docklands Light Railway also passes underneath the Thames between Island Gardens at the southernmost point of the Isle of Dogs, and Cutty Sark in the centre of Greenwich.