I'd want my trains to be able to pass all around my room, but there are windows which would prevent that...
By the way, did you glue your tracks to the shelf cause I'd prefer my tracks to be removable so I can borrow them to the members of the a LEGO club for expos?
My train passes in front of 8 different windows in 2 seperate rooms, I would need to know more about the design of your windows before I can offer advice. 2nd, no, they're not glued, they're screwed, with a #4 guage by 1/4 inch brass wood screw with a tapered head that fit nicely into the mounting hole that LEGO provides when they do their injection molding process... 
