I want to add a second main line to a basic oval Lionel O gauge track plan that I have now.I'm going to use a loop to loop route and because of the confined space for the loops I'm going to use O31 curves. Anyway, when the train enters the loop and goes around to come back on the same track do I need a switch where to two tracks come together? Will I have to activate the switch every time the trains runs around the loop? I want to let the train on it's own. I will use Lionel O31 (6-14062) switches.