Sealston to Dahlgren Laboratory
CSX operates a former Richmond Fredericksburg & Potomac branch east from Dahlgren Junction (just north of Fredericksburg) to just east of Sealston. There are a couple of freight customers near Sealston; this line is north of and parallel to VA Route 3.
East of Sealston the branch was operated by the US Government (US Navy) to support the Dahlgren Laboratory on the western bank of the Potomac River. The US Navy segment has been abandoned for some time, and land in the area is posted "No Trespassing".
The route has been re-opened as a hiking trail, and near the western end there's a short segment of rails over which speeder enthusiasts sometimes ride.
The rail bed from Sealston (actually Bloomsbury Road) to (near) Dahlgren is in private hands and is supported by a "friends" group. Check out the web page: www.friendsdrht.org. (DRHT = Dahlgren Railroad Heritage Trail). The goal is for the trail to be part of the Virginia State Park system, joining the nearby Caledon State Park.