Nothing new here. If you have only two highways (495 and 270), with no east-west flow, you get gridlock, and you get it often. This is no different than a semi flipping over on 495, or a stalled car on Rockville pike, causing bailout to a traffic grid that hasn't been able to handle it for over 20 (30) years. The fact that Potomac was affected is a good thing. Those entitled citizens would never consider a bridge to cross the Potomac River into Tyson Corner to ease such congestion, which is exactly the choke point in this entire region.

Recommended reading: The Giving Tree D