Obviously the only real issue here is running with the pantograph(s) up. Otherwise there's loads of headroom through the 313 for a GG1 with the pantographs down.
Solution: Build 3 sections of catenary on both approaches and through the bridge. Have the fake live wire height at either approach begin higher than the raised pantograph and slowly dip to just below bridge height clearance. The live wire will push down on the pantograph on approach allowing it to clear without fully collapsing and then raise again once the engine has passed through. Of course the middle section of live wire attached to the bridge structure will need to be separate from either end so that the structure can still be raised.
Fun project....one I plan on doing for my fleet of GG1's anywhere there are low bridges, overpasses and tunnel portals. I'll probably end up having the entire layout under wire eventually.
Bruce
