We had an issue come up tonight playing TtR. Nearing the end of the game one player claimed a route, including placing the trains and turning in the train cards, leaving that player with only 5 trains left. That player still needed to claim a 6 train route. Realizing the mistake, the player immediately called for a change in which route he was claiming. This happened BEFORE the next player did anything with their turn. Player in question feels the next player did not start their turn, so it was still his turn and could change his mind. Two other players in the game felt the player's turn ended when he placed his trains and turned in the cards. The player in question lost. There is nothing in the rules. In Monopoly, it is still your turn until the next player rolls the dice. Since there is no clear movement like this, when does a player's turn end in Ticket to Ride?
As far as the game is concerned, you have ended your turn and the next player has been instructed to take theirs. And since the rules say take-backsies are only allowed if... Wait a sec, there are no rules concerning take-backsies in Ticket to Ride. In fact, I've never see a game that allows take-backsies.
It doesn't mean you can't take back the move, but how that works is something your group will have to decide. Personally, I have absolutely no problem with allowing the change since nothing was done based on the move that was performed. But this is my opinion. What your group allows/tolerates is up your group's business.
- One of the expansions has an optional second action you can take. So, in that game, you may not have ended your turn.