Press L to lock an obstacle in place.. there's no way to autolock as the game itself doesnt keep turns or any other indication the game started, that's upt for the players.
As for the collision detection, that is a tricky thing to do in TTS. Before and after performing a maneuver, there's a T button on the dial. This button shows the maneuver template, you should use it to visually check if there was an overlap..

Thanks Johnny :)