How do those lights on the train track turn on? Is there a system that senses the train or is there a certain HQ place that people control the lights?
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Different crossing lights and barriers are operated in different ways.
They can be operated manually by the signaller/crossing keeper (whatever the equivalent is called in your country). This signaller could be situated in a signal box located at the crossing, or could be monitoring the crossing remotely but still activating it. When they know a train is coming they will operate the crossing equipment.
The other option is automatically and there are two main methods by which this can work. One is through track circuits which are devices used for the continuous detection of trains. When the train wheels sit on the rails they complete an electrical circuit between them. This circuit shows the presence of the train to the signalling system, and can operate signalling and level crossing equipment.
The other is a treadle, which is like a switch operated when a train wheel passes over it. A treadle on one side of the crossing causes the lights to engage and barriers to lower, and a treadle on the other side reverses this process.
In either of the last two cases, it is the passage of trains which operates the crossing automatically.
All of these different pieces of equipment form small parts of the whole system, and plug into a system called the interlocking. This is a safety system which prevents train signals from being cleared until other equipment is operated first. For instance, interlocking may not allow the signal protecting a level crossing to be cleared until it is proved that the crossing barriers are lowered.
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