Posted this route a couple of years ago and it's still valid.
The two big obstacles heading south are Fort Belvoir and Quantico. You can take the "official" bike route: Mount Vernon Trail and then Route 1. However Route 1 is VERY nasty to bike on.
A much safer and much more pleasant, but longer route would be to go west to Manassas and come down thru the low-traffic farm country west of Quantico.
My current preference for DC to Fredericksburg:
W&OD to Vienna Community Center
Cherry St, (R) Center St, (L) Locust St, (L) Courthouse Road, (L) Sutton Rd at 2nd TL
Straight on Sutton at stop sign, (L) on Blake Lane, turns into Pickett Rd
Cross Arlington Blvd. First (R) on Old Pickett to T at Old Lee Highway.
(L) Old Lee Highway, (L) University Drive and (L) route 123 to Braddock Road
(R) Braddock Road (headed west) to Old Centerville Road (not Centerville Road / route 28 but the next road)
Stay on Old Centerville Road for several miles (there is a quick L/R at Compton) crossing the river
As Old Centreville is about to end at Centreville Rd / Route 28 go (R) across front of shopping center to Mathis Rd
Couple of miles thru commercial area on Mathis, (L) Main Street, cross under roadraod tracks and (R) Prince William
(L) Wellington, (R) Clover Hill, (L) Hastings, (R) Lucasville Road to get thru Manassas.
take Lucasville to the Bristow Road at Brentsville.
(R at T) Bristow Road
(qL) Old Church, (L at T) Parkgate, (R at T) Aden Road, (qL) Fleetwood / 611
stay on 611, bear right when you come to the rear gate of Quantico
Fleetwood changes to Sowego at the Faquier County line but it is still 611.
(BR) Brentown Road / 612 to Garrisonville Road / 610
I've been out this far several times, but past here my direct knowledge runs out.
Possible routes are 612 and 616 to route 17, just a few miles from Fredericksburg, or go east on 627 to Stafford then route 1 or one of the parallel roads east of it for the last few miles.
I've ridden everything up to 610 and can vouch that it is (mostly) a very good ride (Matis excepted). Trail at the beginning, Suburbs and streets in the middle, towns at Fairfax and Manassas, and mostly rural past Manassas. Sorry for the rough directions but I'm still working on doing a formal cue sheet.
Alternate around Manassas which is simpler but a little longer.
After Fairfax City stay on route 123 (instead of Braddock Rd) and go about 12 mile to Occaquan. The side path and bridge were finished last year and it's a good ride.
After crossing the bridge go (R) into Occoquan and (L) on Washington St (turns into Occoquan Rd)
(R) at Old Bridge. Stay on OB for 4.5 miles (first mile has a lot of traffic, so I usually take the sidewalk until I get to good shoulder.)
(R) onto Prince William Parkway sidepath and go about 8.5 miles.
(L) to stay on PW Parkway when it turns at Liberia, then first (R) on Hastings.
Couple miles to (L) on Lucasville and follow from above.
For a loop you might want to go down by way of Occaqaun and the PWP, and back by way of Manassas. The hills will be a little easier, and there are some good ice cream shops in Manassas you can treat yourself with.
... Possible routes are 612 and 616 to route 17, just a few miles from Fredericksburg, or go east on 627 to Stafford then route 1 or one of the parallel roads east of it for the last few miles.
Stafford to Fredericksburg on US-1 is VERY dicey on a bike. Perhaps even worse than farther north, because the sight-lines become nill in some places, and the shoulder (well ... what shoulder? ... what bail-out plan?).
And if I-95 has an accident or anything, all that traffic gets diverted to US-1.
One can do a series of backroads (lying east of US-1), but it has been a few years since I lived in Fredericksburg, and the only thing I could advise is: it will take some serious amount of time to mapquest / google / yahoo / bikely / whatever to figure out the combination that could work. (Oh, and in that time since I've lived there, the number of houses south of Stafford has sky-rocketed, so be prepared for both pick-up trucks and soccer moms with oversized SUV's.)
oh, and avoid Virginia-3 between Chancellorsville Battlefield and Fredericksburg like it was the plague
I wasn't really recommending Stafford to Fredericksburg on Route 1. Looking at gmap, you could take 630 thru Stafford to Andrew Chapel Rd and Brook Rd to Bel Air.
I was thinking maybe Poplar Rd and switch to Truslow just before it hits route 17. That will get you to Route 1 at Falmouth, only a half mile from the bridge. I'd probably take River Rd to the Route 3 bridge, unless Carl's is open. Then I'd cross the Route 1 bridge and take business 1 to line up for their frozen custard (Carl's has old style machines from the 1950's. People drive down from DC to go there for dessert.)
... unless Carl's is open. Then I'd cross the Route 1 bridge and take business 1 to line up for their frozen custard (Carl's has old style machines from the 1950's. People drive down from DC to go there for dessert.)
We need to help people get their priorities straight:
should always visit Carl's, regardless of the route.
They are usually closed from Thanksgiving to (I think) middle of February.