This is where dasgeh tells you about “the nicest commute in Washington” by taking Irving to 2nd and going through the cemetery via Ft. Myers’ Hatfield Gate. Unless that’s been closed.
If I didn’t take the Ft. Meyer route, I think I would just ride Irving all the up to Wilson, take that to Veitch, hop on the Custis to Key Bridge, and down M/L.
Why good morning. Shawn was almost right — the best commute in Washington is from Fort Myer through the Cemetery — which is still open, but still only allowed in the downhill direction.
Luckily, there is light at the end of the reparing the trail along Rte 50 tunnel, so you have lots of options. None of them involve riding on Columbia Pike for very long — at the very least your friend can take advantage of the lovely bike boulevards north and south of the Pike.