My commute is mostly on the Mt Vernon Trail, from Crystal City to Thomas Circle via the 395 bridge to the Tidal Basin, then up 14th. The trail is almost empty in the morning except for the asian dudes fishing. Can be crowded on nice days in the evenings but not too bad. It's a great commute. Over the last year I've seen Great Blue Herons, Osprey, Bald Eagles, a bunch of other birds, and a pair of Beavers! Beavers!!!