How do train signals know when a train is coming?

A low-voltage electric current is sent between the two rails via a series of relays like the ones in this photo. When a train approaches, the current runs through the train's metal wheels and axles instead of the relays. This short circuit activates the crossing signal.



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At most crossings, the signals will activate about 30 seconds before the train arrives but there are sensors measuring speed so that the crossing knows when to activate; so, the slower the train is, the longer the delay and the faster the train is, the earlier the crossing activates.

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The railway signalling system used across the majority of the United Kingdom rail network uses lineside signals to control the movement and speed of trains. The modern-day system mostly uses two, three, and four aspect colour-light signals using track circuit – or axle counter – block signalling.

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A defect detector is a device used on railroads to detect axle and signal problems in passing trains. The detectors are normally integrated into the tracks and often include sensors to detect several different kinds of problems that could occur.

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Up until the 1980s, this system was also controlled by human operators. However, when computers started to become more commonplace, more automation was introduced. Nowadays, much of the rail signals are automated, and run thanks to a system called CBTC (Communications Based Train Control).

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Train Horn Requirements Train horns must be sounded in a standardized pattern of 2 long, 1 short, and 1 long blasts.

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Well before the train gets anywhere near the station it has lights that tell it to slow down, and stop. Depending on which lights are lit, depends on the drivers actions. Red and green are the same as normal road lights… stop or prepare to stop, and go or keep going.

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There are countless reasons never to walk, run or play on rail tracks and rail property. Most people don't know it can take more than a mile to stop a train — the equivalent of about 18 football fields. That makes it difficult, if not impossible, for a train to stop if someone is on the tracks.

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By the time a train operator sees you, it is too late to stop the train in time. An oncoming train is moving faster and is closer to you than it appears. Similar to an airplane traveling at 150 mph that appears to float onto the runway, it's hard to determine a train's speed and distance from you.

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Driverless trains have been in operation on the Docklands Light Railway since it opened in 1987, though a train attendant is present to operate the doors and drive the train if needed.

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Automation of London Underground rolling stock has been partially implemented since the introduction of automatic train operation on the Hainault to Woodford section of the Central line in 1964. It is currently in use on six lines. Transport for London plans to extend this to remaining lines by 2023.

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Defective or damaged track circuits and axle counters are leading causes of signal failures. Damage to these components can be caused by moisture penetration, cuts, exposure to high temperatures, or rusting. In some cases, the damage may be caused by cable thieves who have pilfered cables for their copper content.

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Why do trains sound their horn? Federal law requires the train crew when approaching a road crossing to sound the horn at all public crossings for the protection and safety of motorists and pedestrians regardless of whether crossings with gates and lights are present.

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Over-fatigued drivers and utility workers present a hazard. Waving means you're at least half awake and alert enough to notice a fellow laborer and therefore respond safely if something unexpected happens.

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