My girlfriend told me. She once worked as a guide on the train "Moscow-Vladivostok". When the train went along the coast of the Baikal, sometimes the driver slowed down, giving the opportunity to quickly plunge into the Baikal brigade.
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You are like children. Sometimes the train (not fast, simple) stands in general in a clean field, in the middle of a race. This is called "pass the meeting fast", for example. Further roads will be single-rail or bridge, for example, and this parking is specially included in the schedule. And it happens, the driver is ahead of the schedule, but on the next ride, no one will miss it outside the schedule, and it slows down where it is possible and pleasant. He may be specifically ahead, but never at the expense of the schedule. For the breakdown of the schedule without very serious reasons not dependent on the railway, the locomotive brigade will hardly appear.