That said, you'll still have what I mentioned earlier. It's all going to be Blue Line. No Yellow on the Green, it'll make no sense. You *may* get a Yellow up to Regan National, use that middle track for the turn-around point... which gets into some operational questions: Would they open all the doors? Or would they open the Northbound side first, empty it out, close it, open the Southbound side for those waiting to get on, close, and go back. I can see the latter being safer.
Likely open to the northbound side first as that is the side the train is being operated from then open the southbound side. The operator making the return trip south might end up opening the doors on the southbound if the operator that brought the train in from the south did not open them before leaving the cab of the train..
John in the sand box of Maryland's eastern shore.