DC and "city repair" of the urban grid
A number of cities around the world have done this in various ways -- getting rid of freeways more generally (San Francisco's Embarcadero Freeway, Milwaukee, Boston's Big Dig, Seattle's Highway 99, albeit because of earthquake risk), along waterfronts (Portland, Oregon) or restoring rivers that had been covered up (Seoul) and/or tunnelizing major freeways (Marseille, Thessaloniki, Madrid) -- or have proposed doing so.
Note that this is expensive to do, but might be cheaper than the cost of rebuilding freeways at the end of their useful life. Generally, it's "affordable" in central business districts with high property values, when "new land" created supports new high intensity development.
And DC has decked some sections of the I-395 Freeway, including the most recent "Capitol Crossing" project.
Foggy Bottom as an opportunity. Greater Greater Washington reprinted an entry that discusses a 1997 proposal to do this in Foggy Bottom, which is cut up by arterial tunnels, a stub of I-66, and the Whitehurst Freeway. Kennedy Center, the performing arts complex, is a kind of an island in the midst of roadways.
When I suggested that decking be employed with regard to the Southeast-Southwest Freeway, I was definitely remiss in not mentioning the similar opportunity in Foggy Bottom. (Although the FB article doesn't discuss the poor placement of Kennedy Center from the standpoint of what Jane Jacobs called "mixed primary use" and her example of the creation of a standalone arts district in the Oakland neighborhood in Pittsburgh, rather than downtown.)
City Repair organization in Portland, Oregon.
Cities should create "Urban Design Opportunity Plans." Most cities have plenty of opportunities for "city repair" and urban design advocacy agendas for such, applying the "Transformational Projects Action Planning" approach, should be developed, at the city-wide scale more generally, and at the neighborhood scale, like the way I suggested for the Dupont Circle neighborhood in DC or Silver Spring, Maryland:
-- PL #5: Creating a Silver Spring "Sustainable Mobility District" (2017)
or what Alexandria, Virginia is doing around its waterfront, at the foot of King Street, or for more pedestrianized areas within cities like Las Ramblas in Barcelona or the plaza program in New York City.