Some buses have been re-routed as traffic delays continue.
D.C. police have closed the road between Delafield Place and Emerson Street.
First Street on east side of Capitol was closed due to bag left at Library of Congress.
But speeding up the opening also means a traffic shutdown at the bridge this weekend.
D.C. Water is looking into a water main break.
One lane on Virginia Avenue NW will remain closed while crews continue to work on the portion of the Watergate garage that collapsed May 1.
The two buses hit each other at 5:38 p.m. near Massachusetts Avenue NE.
The area has been closed since last Friday's garage collapse at the Watergate complex.
Many rush hour drivers will be slowed by the narrowing of an I-395 exit ramp.
The program beginning Friday targets 650 intersections in the District's core.