If you are trying to get around using public transportation systems, there are plenty available. You can get almost anywhere inexpensively and with minimal walking.
This handy trip planner will compute a route to your destination from wherever you happen to be and will make use of any available mode of public transportation except taxis and charter buses.
Loudoun County Transit operates rush hour service from park and ride lots in Loudoun to destinations that include West Falls Church Metro, Rosslyn, the Pentagon, and Washington, D.C. Loudoun County Transit also provides service from West Falls Church