One reply suggested the W&OD to Front Royal, Va.I drive the route over the mtn on rt 50 or rt 7. Both are major high speed commuter routes with narrow to no shoulders. I cringe with horror when I see a touring cyclist on these roads. I have considered stopping to offer a ride up and over, but there is NO place to pull over. There are safer times to ride these routes, but still expect high speed traffic.
FWIW, I put Purcellville (the end of the W&OD) and Front Royal into google maps, hit the bike route icon, and the route it popped up included 3 miles on 7 and 4 miles on 50. Call me a flaming optimist, but I think that's reasonable for a 40 mile leg. With any luck you could be going against commute traffic in the morning and get into Front Royal before the afternoon rush hour strikes. (Fridays before federal holidays excepted, of course!)