Trowse Bridge
Encyclopedia
Great Eastern Main Line
The Great Eastern Main Line is a 212 Kilometre major railway line of the British railway system, which connects Liverpool Street in the City of London with destinations in east London and the East of England, including Chelmsford, Colchester, Ipswich, Norwich and several coastal resorts such as...
over the River Wensum
River Wensum
The River Wensum is a chalk fed river in Norfolk, England and a tributary of the River Yare despite being the larger of the two rivers. The complete river is a designated Site of Special Scientific Interest and Special Area of Conservation ....
just outside Norwich
Norwich
Norwich is a city in England. It is the regional administrative centre and county town of Norfolk. During the 11th century, Norwich was the largest city in England after London, and one of the most important places in the kingdom...
in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
at .
The bridge was originally built in 1845 by George Parker Bidder
George Parker Bidder
George Parker Bidder was an English engineer, architect and calculating prodigy.Born in the town of Moretonhampstead, Devon, England, he displayed a natural skill at calculation from an early age...
, and was rebuilt in 1906 and again in 1986. Unlike most swing bridges in operation, Trowse is possibly unique in that the structure lifts on hydraulic jacks before swinging open to allow the passage of water traffic. The bridge has frequently caused problems with navigation on the river due to its unreliability, leaving it unable to open.
It is notable for being the only swing bridge
Swing bridge
A swing bridge is a movable bridge that has as its primary structural support a vertical locating pin and support ring, usually at or near to its centre of gravity, about which the turning span can then pivot horizontally as shown in the animated illustration to the right...
in the United Kingdom to carry an overhead electrified railway
Railway electrification system
A railway electrification system supplies electrical energy to railway locomotives and multiple units as well as trams so that they can operate without having an on-board prime mover. There are several different electrification systems in use throughout the world...
track (25kV 50Hz
25 kV AC
The 25 kV Alternating current railway electrification system is commonly used in railways worldwide, especially for high-speed rail.-Overview:This electrification system is ideal for railways that cover long distances and/or carry heavy traffic...
). (Other examples can be found along the Northeast Corridor
Northeast Corridor
The Northeast Corridor is a fully electrified railway line owned primarily by Amtrak serving the Northeast megalopolis of the United States from Boston in the north, via New York to Washington, D.C. in the south, with branches serving other cities...
in the United States; see for instance Portal Bridge
Portal Bridge
The Portal Bridge is a rail bridge over the Hackensack River just west of Secaucus Junction in northeastern New Jersey, USA. The two-track, moveable swing-span between the towns of Kearny and Secaucus is owned and operated by Amtrak...
.) The overhead supply to trains is provided by a rigid bar rather than a wire, and there are short lengths of rigid bar either side of the bridge on the fixed approaches. Trains normally travel at quite low speeds over the bridge (because they are just about to arrive at, or have just departed from, Norwich).
The bridge is also the home of Trowse Signal Box
Signal box
On a rail transport system, signalling control is the process by which control is exercised over train movements by way of railway signals and block systems to ensure that trains operate safely, over the correct route and to the proper timetable...
. This controls most of the Bittern Line
Bittern Line
The Bittern Line is a railway line from Norwich to Cromer then Sheringham in Norfolk, England. It is one of the most scenic in the East of England traversing the Norfolk Broads on its route to the Area of Outstanding Natural Beauty on the North Norfolk Coast. The line is part of the Network Rail...
from Whittlingham Junction to Sheringham
Sheringham railway station
Sheringham railway station is a timber halt in the town of Sheringham in the English county of Norfolk. The station is the terminus of the Bittern Line, operated by National Express East Anglia, and is 49 km north of...
. The line was resignalled in 2000, leading to the closure of a number of mechanical signal boxes with control moving to a Trowse, although it is arguable if this is a real improvement since there have been a number of serious failures causing full or partial suspension of service during electrical storms. This is due to the system using high frequency pulses in the rail as opposed to standard track circuits to operate level crossings. This saw the end of one of the few remaining sections of single track main line controlled by tokens. The signalling meant Cromer Signal box that the last surviving M&GN example was decommissioned; however it has been saved as a museum.