I'm working on a project to map the 1921 passenger system around DC and Baltimore in 1921 in a subway-map style (details here) but there's only so much the Official Guide to the Railways can tell me. One particularly sticky point is how trains used to run to Front Royal. It's a one-stop branch off another branch. Would this have been handled with shuttle trains to Happy Creek and/or Riverton Junction? Would trains have diverted to Front Royal then returned to the mainline? I can provide other info and screenshots if needed.