The game moves towards its end once a player has “6 or fewer pieces”. Question: are the “harbor” pieces included in this count or only “locomotives” and “ships”?
It only includes Ships and Trains. The English rulebook is a bit unclear on this point, but other translations make it clear.
The specific wording form the English rulebook:
When any one player’s supply of plastic pieces contains six pieces or fewer (regardless of their type), each player, including that player, gets two more turns, after which the game ends and players calculate their final scores.
Note that "plastic pieces" is also used in the rulebook in other places, such as when talking about exchanging pieces. Because you start with all your harbor pieces anyway; you would never need to exchange them; you are only exchanging trains for ships or vice-versa.
From the French rulebook:
Lorsque la réserve de wagons d’un joueur tombe à 6 pions (wagons et bateaux confondus).
When a player's wagon reserve drops to 6 pawns (wagons and ships combined)
Wenn ein Spieler am Ende seines Zugs nur noch 6 oder weniger Figuren (egal ob Waggons und/oder Schiffe)
If, at the end of his turn, a player has only 6 or fewer pieces (regardless of whether they are wagons and / or ships)