I have a feeling this was already considered by Fairfax Connector et al., but I'm wondering if it might be feasible to have bus contingencies for when Metrorail service is interrupted.
The Friday after the blizzards was a good example of What Life Would Be Like Without Public Transit in west county at least. The Orange Line was only going to Ballston so all the feeder buses didn't run even though major roads, such as I-66, seemed fine. (Had they run they would have hit horrific traffic like we all did.)
But what happens when there's any kind of track issue on the Orange Line? Do buses have a contingency if Vienna or WFC aren't operational?