Welcome to the board, Simon.
It's not so hard to push boats on land, but uphill is tricky because it wants to go to one side and slide down. I pushed a derailed locomotive through the whole city to make a "roadblock" on the railway but it didn't work. Only one locomotive can be present at one time, and the game do count derailed locomotives. I didn't think of putting it in a garage.
OT: Simon has a postcount of 0, isn't this forum counting posts?