The four rail system was first used in the early twentieth century. The isolated traction current return allowed a train’s position to be detected using DC track circuits, and reduced any earth leakage currents that could affect service pipes, telephone cables, or cast iron tunnel liners.
What does the 4th rail do?
The 4th rail in electrical rail systems is to prevent stray currents from corroding 3rd party buried services in the vicinity of the railway system such as iron pipes. The 4th rail system is not needed for tram cars on the high street because tram cars draw for less current than London underground trains.
How many rails are there on the underground?
The railway infrastructure of the London Underground includes 11 lines, with 272 stations.
Does London Underground have third rail?
All London Underground Lines (including the W & C) operate at 630 volts DC using third (positive) and fourth (negative) current rails. The current rails are positioned so that the contact surface is higher than the running rails.
Why is the third rail electrified?
The running rails are electrically connected using wire bonds or other devices, to minimise resistance in the electric circuit.
Why do some train tracks have 4 rails?
A quadruple-track railway (also known as a four-track railway) is a railway line consisting of four parallel tracks with two tracks used in each direction. Quadruple-track railways can handle large amounts of traffic, and so are used on very busy routes or sections. Such conversion is referred to as “quadruplication”.
What does the 3rd rail do?
When we talk about the third rail, we mean the live rail which provides electric power to a train through a conductor placed alongside the rails. Nearly half of the UK rail network is now electrified – and more than 30 percent uses a third rail to power the train.
Which Tube line is deepest?
The deepest station is Hampstead on the Northern line, which runs down to 58.5 metres. 15. In Central London the deepest station below street level is also the Northern line. It is the DLR concourse at Bank, which is 41.4 metres below.
What to do if you fall on the Underground tracks?
Try to climb out with the help of someone who can help hoist you. Lie down between the tracks, depending on the depth of the tracks. Get to the side of the track. Step between the girders that separate tracks (but this involves stepping over the third rail, which carries more than 600 volts of electricity).
Can you get electrocuted on Tube tracks?
Both positive and negative rail are equally capable of electrocuting you, and you don’t need to be touching both – you just need to provide a path from one to ground (which you almost certainly will if you are touching anything else).
What happens if you touch third rail?
Touching a third rail can result in electrocution, so usage of the metaphor in political situations relates to the risk of “political suicide” that a person would face by raising certain taboo subjects or having points of view that are either censored, shunned or considered highly controversial or offensive to advocate
Which is the oldest Tube line?
Metropolitan line
Metropolitan line
Opened in 1863, The Metropolitan Railway between Paddington and Farringdon was the first, urban, underground railway in the world.
What is the longest London Underground line?
The Central Line
The Central Line was opened in 1900 and is forty six miles long, making it the longest line of the system, between the stations of West Ruislip and Epping. The Central Line is one of only two lines which have stations outside the boundaries of Greater London.
Do rats touch the third rail?
But rats have been observed running on the third rail and jumping off without being electrocuted.” The transit system uses a variety of poisons and other weapons against rats, but experts say there is only one foolproof way to reduce their population: don’t feed them with trash. Q.
What happens if you touch a train track?
“The electricity is so strong that if you touch the rail or step on it, you will stick to it like glue and won’t be able to get off. “The electricity is likely to kill you – and, if you do survive, you will suffer terrible burns.
Why do so many cars stop on train tracks?
One thing that can happen is, the rails can get to be higher than the road crossing them. This can be caused by the road settling or th tracks becoming higher because of trackwork, including placing more ballast to the railbed. This condition could cause a car or truck to get hung up on the rails, unable to move.
Why are train tracks lined with gravel?
It is used to bear the load from the railroad ties, to facilitate drainage of water, and also to keep down vegetation that might interfere with the track structure.
Why do trains not derail?
The train maintains tractive effort, which is the weight given by the engine and due to this the wheel of the train does not slip. Actually, the special system of the railway always keeps the force applied by the engine on the wheel less than the limit of frictional force, due to which the engine does not slip.
Can you walk on the third rail?
Never walk or run on the railway track – you can’t tell which rail is electrified. Always use a level crossing to cross the railway. Never ignore a railway sign or a railway worker.
What is the fourth rail?
fourth rail (plural fourth rails) (rail transport) An extra rail in addition to the third rail (live rail) which is used for current return purposes, mainly by London Underground, because of problems caused by using the running rails for current return underground.
Why do trains have three headlights?
To summarize: It is so that road and rail vehicles can easily be distinguished from each other at night, from a distance. Note that different countries have different regulations for train lights.