The South Capitol Street
Underpass at M Street

South Capitol Street Underpass at M Street

This underpass was planned in the 1950s, and completed by the early 1960s. It’s most similar structure in Washington D.C. is the North Capitol Street underpass beneath New York Avenue (below).

North Capitol Street Underpass at New York Avenue

It carries two lanes in each direction for South Capitol Street traffic, descending and ascending between N and L Streets, with a 3^rd lane per direction proceeding through an at grade surface traffic light intersection with east-west surface M Street.

To its south, South Capitol Street has a median barrier to prevent all lateral access- both vehicular and pedestrian, with no traffic lights to the South Capitol Street Bridge. IOW no one may cross the street. But also, no one has to stop at a traffic light to get to the north of M Street, with right hand (but not left hand) turns allowed onto P, O and N Streets.

The two above illustrations are from the web site of the National Association to Restore Pride in the Nation's Capital:

http://www.narpac.org/REXLRPRO.HTM