Crews will close a southbound lane of the 9th Street tunnel in downtown Washington, D.C., beginning on September 28, 2026 and lasting until June 30, 2027. One outer lane will remain closed around the clock, while the center lane will be subject to limited closures of up to six hours.
The tunnel runs beneath the National Mall near Constitution Avenue NW, and the lane closures are part of a repair project that will affect traffic flow through the downtown area for the nine‑month period.