I think you must have pissed off someone at Google, because it looks like there are trying to kill you.
Centreville Rd? Nokesville Rd? Route 17?

I’d take Old Centreville instead of Centreville Rd?
Nokesville Road used to be sleepy country lane, but in the past 10 years it has become a major highway. Better to take Lucasville out of Manassas to the quiet country roads aroudn Brentsville and Aden. Skirts the west edge of Quantico.
Route 17 to Falmouth has a rideable shoulder, but the road is a busy-scary mess. Truslow would be better, that way you deal with just a short piece of route 1.
Their route through Fredricksburgh is ok, but route 17 south is not. From Fredricksburgh to Port Royal it is one narrow lane each way, busy, lots of blind curves and lots of trucks. It is VERY dangerous for a bike.
Past Port Royal it is a divided highway. Still busy but there are shoulders for much of it.

Route 17 would be the shortest route, but I’m not sure it is the best. Are you going to try it in one day? What time of year?
I’ve been wanting to check out route 2 to Bowling Green and route 40 to West Point. Looks doable and I’ve heard from others who ride that area that it is not bad.

There have been discussions on the forums on how to get to Fredricksburgh and Williamsburg. Here’s the link to a couple of them (I’ve got some maps posted in there)

http://www.bikeforums.net/showthread...ght=Lucasville
http://www.bikeforums.net/showthread...hlight=ashland

Good luck.