DennR refers to locking the Route layer when creating sessions, EXTREMELY wise. HOWEVER be very aware (doesn't apply to DLC cause you can't unlock them), that it you exit and come back later to do some more editing of the session, the route layer will be UNLOCKED! This is a serious flaw in the game (from day 1?) which for some strange reason N3V will not address. Are you listening N3V? You really REALLY need to make the default Locked, not unlocked. Massive headache right there...