Close by the Van Dorn Street Metro station on the Blue Line is a Norfolk Southern facility. At the end of the Metro parking lot away from the station, a public road goes right next to the tracks. There usually is power tied up there, though the trains are infrequent.

In Manassas, about a mile west of the railroad station in town (you can ride there on weekdays using Virginia Railway Express) is another Norfolk Southern facility, with something almost always going on. A public road crosses the mainline and another crosses two legs of the wye.

Not a yard, but with a pretty high density of freight traffic, is the Alexandria railroad station, adjacent to the Metro King Street station. Lots of CSX freights, a few Norfolk Southern freights, and lots of passenger trains too, not to mention rest rooms, vending machines, and benches. It's a popular spot with railfans.