If US 1 still runs 14th/Constitution/6th/Rhode Island, I could find zero shields at any of those intersections in GMSV.
US 50 is signed where soon-to-be-renumbered I-395 ends at it and further east.
It was once possible to follow U.S. 50 and U.S. 1 across D.C. with the signs.
Eastbound 50 from Arlington County went T. Roosevelt Bridge to Constitution Avenue, N.W. to a left on 6th Street, N.W. to a right onto New York Avenue, N.W (and New York Avenue, N.E.) out to the Prince George's County, Maryland border.
Westbound was mostly a reversal of the above, though U.S. 50 westbound used L Street, N.W. from a point after the I-395 tunnel entrance to a left onto 6th Street, N.W. to a right onto Constitution Avenue, N.W. to the T. Roosevelt Bridge.
U.S. 1 northbound came across the 14th Street Bridge, up lower 14th Street, S.W., then 14th Street, N.W. to a right onto Constitution Avenue, N.W. Then a left onto 6th Street, N.W., following that to a right onto Rhode Island Avenue, N.W., then Rhode Island Avenue, N.E. out to the Prince George's County, Maryland border.
Southbound reversed the above, save for heading west on Constitution Avenue, N.W. to a left onto 15th Street, N.W. to Jefferson Drive, S.W. to a right onto 14th Street, S.W.