Immediately south of Alexandria Union Station (MP 8.2), where there is a road bridge overhead, the line turns to the west, past crossovers at Pepco. and the route taken by the Crescent Limited and the Manassas VRE trains diverges on both sides at AF Tower (MP 9.1), with speed limit 45 mph to MP 11.0, and then the track on the south side passes under the RF&P line to head west while the RF&P turns again to the south. As far as Manassas, the route is shared with Virginia Rail Express, an operator of commuter trains to Washington DC.
After passing under the ex-RF&P, the south track of the ex-Southern route continues west past Cameron Run and a bridge over a river to CR Tower (MP 10.7), where the track from AF Tower along the north side trails in from the east, with a signal bridge, extra track on the north side, crossovers, a signal bridge and a road bridge overhead, and the now double-track line, with speed limit 79-60-50, turns west-southwest, past the Van Dorn Street Intermodal Terminal on the south side, where there are crossovers, and continues curvily east past a big road bridge overhead, Edsall, (MP 12.9), where there are crossovers and extra track on the north side on the grounds of an industry, a bridge over a river, an array of big satellite dishes to the north, a road bridge overhead, the south side (only) platform of a VRE passenger station at Blacklick Road, extra track on the south side, and crossovers at Springfield
There is a speed limit of 60-50 from MP 14.0 to 17.0 and 50 mph thence to MP 18.5, a group of six road bridges overhead at the I-95 interchange, a VRE station on the south side, spur tracks on the north side, Intermediate Signals at South Springfield, a main road bridge overhead, extra track on the north side, housing in the woods on the north side, Intermediate Signals at Raymond, a road bridge overhead, a bridge over a stream below (leading to a lake), Intermediate Signals, woods on the north side, a spur trails in on the north side, a road alongside to the south, detectors at MP 18.8, a road bridge overhead, a VRE passenger station at Rolling Road (south side platform only), a road bridge overhead, crossovers at Burke (MP 19.9), where the speed limit is 55-50 and there is an extra track, MP 20.1, where the speed limit falls to 50 mph to MP 20.3, where 55-50 resumes, a VRE passenger station (south side platform only) at Burke Center, a spur on the north side trails in, a road bridge overhead, extra track on the south side serving industry on te south side, Intermediate Signals at Crestwood, dual road bridges overhead, more woods on the south side, extra track on the north side, dual road bridges overhead, and Intermediate Signals at Fairfax (MP 23.5), where the speed limit falls to 50 mph
The line turns southwest, past woods on the north side and a bridge over a stream, and then west past a grade crossing just north of the signal bridges and crossovers at Clifton (MP 26.8), where there is extra track and a spur trails in on the north side, a stream alongside to the south, a bridge over that stream, south, with speed limit 40 mph on the curve, past Intermediate Signals at Bull Run, a VRE passenger station at Manassas Park (south side platform only), where the speed limit is 50 mph to MP 30.7, where it becomes 70-50, past a grade crossing, a spur turning away on the north side, a road bridge overhead, detectors at MP 31.6, two grade crossings, cantilever signal bridges and crossovers at Moore, with extra track on the north side, and two grade crossings, and southwest past an Amtrak and VRE passenger station (depot buildings to the north and south (brick), two side platforms with umbrella sheds) at Manassas (MP 32.8), with a grade crossing within the platforms, and a bridge over a road west of the station, and then west to Manassas Junction (MP 33.0), where the line to Front Royal and Strasburg heads north at a wye, the east leg of which is behind the yard tracks on the north/west side, and then west, while the main line turns southwest.