One person died in the two-car collision.
What did Mark Kawar do on his day off? He rode Metro -- all day and all night long.
Police said crews are working to clean up the crash, but as of 7 a.m. traffic was still backed up on the highway.
Metro said residual delays to Mount Vernon Square station on the line because of an earlier train malfunction were resolved.
After simulating Silver Line service all day Sunday and Monday morning, transit authority says the new rail route is glitch-free so far.
Police said there were normal rush-hour traffic delays on the highway after a backup that stretched from Frederick to Montgomery County after an accident.