I doubt the streetcar will ever amount to much. The only streetcars I've ever ridden on have been in Boston (Green Line) and Europe. In all of those instances, the streetcar had its own right-of-way for most of the time.
DC would have been better suited to institute rush-hour HOV/bus lanes on major corridor (16th street Silver Spring, Penn Ave, etc) and kept to that. Could have folded over nicely into a region-wide BRT network.
D.C. once had a very good streetcar network.
Some of the lines (ironically including the one on H Street, N.E.) were converted to bus service
because the streetcars could not keep up with demand (the H Street/Benning Road line went in 1947, the first postwar abandonment of streetcar service in D.C.).
Before World War II, streetcars on Connecticut Avenue, N.W. (and into Chevy Chase, Maryland and beyond to Kensington) were converted to bus, as was a line that ran north from Wisconsin Avenue and Western Avenue - it roughly followed Wisconsin Avenue/Rockville Pike to downtown Rockville; and the Washington, Baltimore and Annapolis (WB&A) interurban line was shut-down due to bankruptcy in 1935 (the big WB&A cars ran into D.C. from Seat Pleasant to downtown over the streetcar system's rails, including Benning Road and H Street, N.E.).
In 1956, after a
nasty transit strike, Congress revoked the transit franchise from Louis Wolfson's Capital Transit Company (CTCo) and awarded it to O. Roy Chalk's D.C. Transit System, Inc. Chalk's company was
required, as a condition of taking the transit franchise, to abandon the entire streetcar system by the early 1960's and run a bus-only system. Chalk wanted to keep the streetcars running (the tracks and cars were in good condition), but did as he was told (remember there was no elected local government in D.C. of any kind back then), and the last of the streetcars rolled on D.C. streets in 1962.