[whoopdedo]

There isn't enough highway in DC to make express lanes worthwhile.

The benefit of HOV on 395 & 66 comes from having limited access. The lanes get crowded during rush hour, but they still move faster because of less merging & exiting. When traffic is all moving in the same direction at the same speed it flows smoother.

The changes to the Springfield interchange did a lot to prevent backups by reducing the amount of lane changing necessary to get on and off the Beltway.