I've found a hidden feature inside the factorio modding API, this mod turns it on. It gives you a whole new perspective on trains. See https://youtu.be/5nRnnfKMZKQ for an example about what it does.
The shift in late November 2021 was caused by a change in the way we count mod downloads. A download is counted when a user downloads a specific mod release for the first time. We take in-game and web downloads into account.