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Ok so. When you look in videos(or in real life) with the railroad signals, when a train passes over it, it takes around 3 to 5 seconds for it to actually change to the correct aspect. What is up with that?

user3831089
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    Can you provide a source video for this? I haven't seen this in the UK. Perhaps it's just a time-lag to make sure the train really has gone past the signal, rather than just reached it? – Jonathan R Swift Jan 08 '18 at 14:30
  • If you're looking at "all-clear" signals, they are generally switched immediately when the train passes a signaling switch far up-road. – Carl Witthoft Jan 08 '18 at 18:33
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    What possible content is the initial "Ok so." supposed to provide? Stop and actually think about what you are writing. – Olin Lathrop Jan 10 '18 at 13:26

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Its for safety. Electric trains especially can create lots of freak currents on the train tracks that may or may not cause false detections, so you want to be sure that the train detection has been triggered for several seconds continuously instead of by just a single short pulse.

MadMarky
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