VRE has two lines, the Manassas Line and the Fredericksburg Line, starting at Manassas and Fredericksburg, Virginia (what a shock, it actually makes sense). Most trains run toward DC in the morning and away from DC in the evening, but a couple trains per cycle run in reverse to take reverse commuters from the city to their jobs in the suburbs.

There has been much talk about extending the Fredericksburg line further down I-95 to Richmond, but no real action yet.

The VRE trains run in a push-pull configuration; they go backward on inbound runs and forward on outbound runs. They hold the trains at three yards at either end of the line -- in D.C., the yard in question is the Amtrak facility at Ivy City, and serves both lines. In Manassas, there's a small yard just past the Broad Run/Airport station; on the Fredericksburg line, VRE uses the Crossroads yard just south of Fredericksburg station.

Also, VRE now goes to Richmond, sort of, using a bus bridge provided by the GRTC Transit System. Actual rail service to Richmond is still years off, though.