Editing Interstate 66 (section)

===Washington, D.C.===
[[File:2018-10-25 13 51 18 View west along Interstate 66 (Potomac River Freeway) from the overpass for Triangle Park-Virginia Avenue-New Hampshire Avenue-25th Street in Washington, D.C..jpg|thumb|The Potomac River Freeway (I-66) in Washington, D.C.]]
[[File:I66toscale.png|thumb|right|500px|A map of I-66, showing cities and interchanges with [[Interstate 81 in Virginia|I-81]] and [[Interstate 495 in Virginia|I-495]]]]
In Washington D.C., I-66 was planned to extend east of its current terminus along the North Leg of the [[Inner Loop (Washington, D.C.)|Inner Loop]] freeway. I-66 would have also met the eastern terminus of the planned [[Interstate 266|I-266]] at US&nbsp;29, and the western terminus of [[Interstate 695 (District of Columbia)|I-695]] (South Leg Freeway) at US&nbsp;50; I-266 would have been a parallel route to I-66, providing more direct access to the North Leg from points west, while I-695 would have been an inner-city connector between I-66 and I-95.

The final plans for the North Leg Freeway, published in 1971, outlined a {{convert|1.5|mi|km|adj=on}} six-lane tunnel beneath [[K Street (Washington, D.C.)|K Street]], between I-266/US&nbsp;29 and New York Avenue, where the North Leg would emerge from the tunnel and join with the [[Center Leg (DC)|Center Leg Freeway]] (formerly I-95, now I-395); the two routes would run concurrently for {{Convert|0.75|mi|km}} before reaching the [[Washington Union Station]] interchange, where I-66 was planned to terminate. Despite the plan to route the North Leg in a tunnel beneath K Street, the intense opposition to previous, scrapped alignments for the D.C. freeway network, which included previous alignments for the North Leg Freeway, led to the mass cancelation of all unbuilt D.C. freeways in 1977, resulting in the truncation of I-66 at US&nbsp;29.
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