The Signalling Record Society
Railway Bridges & Tunnels
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Signal Fact 15
E A Cowper invented the railway detonator in 1841. Used to protect trains that had come to a stand unexpectedly.
First adopted by the Great Western Railway, the other companies soon followed suit.
Detonators are still used today.
Bridges and other similar structures are generally numbered in sequence along a specific railway line. Included in the number sequence are over bridges, under bridges, foot bridges, intersection bridges (where two lines cross), side bridges such as retaining walls (not actually passing over or under the line), tunnels and subways.
Railway companies usually started their bridge numbering at one end of the line and continued in straight numerical sequence along the line. In most cases a separate number series existed for each line, thus most railway companies had more than one bridge 1 and so on. Renumbering of bridges is relatively rare but not unknown.
Most number sequences date from the building of the line although with the passage of time and loss of some bridges there are now gaps in many sequences. Long routes which are generally seen as 'one line' today often have several sequences of numbers with the 'restart' positions echoing ancient boundaries between the original owners of the line.
The most notable exception to the general practice was the Great Western Railway which numbered each structure using the relevant milepost mileage. This practice continues to this day on the Western Zone of Network Rail. Bridges transferred by British Railways from the Western Region to the London Midland Region in the course of regional boundary changes were then given a numerical numbering sequence by the new 'owner'. The London Brighton and South Coast Railway also used mileages to designate bridges, etc, and this practice continued through the Grouping and into the BR era before a numbering scheme was introduced
Where additional structures were added after the initial numbering exercise, each additional structure received the number of the bridge immediately preceding plus a suffix letter. Thus a new bridge added between bridges 1 and 2 would be 1A. The suffixed numbers were allocated in date order of construction and thus a situation of additional structures added from time to time can give rise to a sequence such as 1 1A 1C 1B 2 and so on.
In or about 1909 the Great Eastern Railway renumbered all its bridges in a single, company wide, number sequence. A copy of the bridge numbering book from that time can be obtained from the Great Eastern Railway Society.
Many bridges had names associated with them and these names generally survive to this day in Netowrk Rail's official lists. More recent bridge number plates include additional information and this has resulted in some names reappearing in 'public' long after the old name had disappeared from local memory. Thus there are very old names for roads (or tracks or lanes) mentioned despite the road being renamed by the local authority a century or more ago. Some bridges on 'A' roads even sport the long lost name of a local farmer where the origins of the bridge are as an occupation or accomodation provision when the line was built.
Current Network Rail practice is to generally number each structure in three places - facing the driver of any approaching train from either direction and one visible from the roadway - adding in the Engineers' Line Reference and the milepost mileage. Roadside information also includes a contact telephone number for emergency reporting and the name. Not all bridges comply with this policy, particularly footbridges and subways within a station.
A unique structure reference is thus generated using a combination of ELR and bridge number or, similarly, using a combination of RailRef and bridge number.