IF you're going to hinge the track, the center line of the pivot pin on the hinge needs to be above the top of the rail. The first "up" motion with this geometry, the ends of the track moves apart. Otherwise, you'll need an additional gap so the track doesn't hit.
Wire power to the rails and it doesn't matter if there's a gap at each end. Safety interlocks (relays) are prudent, but not required. The risk is when (not if) your engine takes the big dive off the edge because you forgot and left the bridge "up".
For your curved bridge, scribe a line parallel to the edge of your benchwork and cut,
