Tried to do something I hadn't done in a while and just ride a train. Was on Northern Trans Pennine. I noticed that all the passengers got off at the Leeds station, and none boarded. Then I noticed that every seat was empty on all the cars, and I was unable to sit in any of them. The train departed the station completely empty. It appears none of the seats are able to seat passengers, both player and AI. I could open every door, but sit in none of the seats. I believe this used to work prior to the update.
Already been reported to and noted by DTG, when we get a fix is another matter though. https://forums.dovetailgames.com/threads/passenger-mode-i-cant-sit-down.59469/