From the South Capitol EIS:
As a primary corridor in L’Enfant’s 1791 Plan for the City of Washington, South Capitol Street was envisioned as one of the symbolic gateways to the city and its Monumental Core. ... Today, South Capitol Street lacks any characteristics of its historic and intended function as a gateway. ... South Capitol Street is an urban freeway that has become a conduit for through traffic at the expense of serving the needs of residents and businesses in the corridor. The transportation infrastructure is obsolete, in deteriorating condition, and fails to provide necessary connections to community destinations for pedestrians, bicyclists, transit riders, or motorists.
DC will be restoring South Capitol as a grand gateway and make it a street worthy of the new neighborhoods replacing the industrial uses in that section of the city. They just released two final alternatives, which can be basically summarized as better and even more better.
Both alternatives reduce many of the worst elements of suburban traffic design in the region. The Southwest/Southeast Freeway is enormously urban-unfriendly as it is, and it has large, curving ramps for traffic to get and on off from South Capitol. Both alternatives seek to replace the northbound on-ramp, that crosses over South Capitol, with a shorter ramp that cars access by turning left from South Capitol.
Today, medians block cross traffic on many of the streets, making it easier for people to drive through but harder for people to get in and out of the surrounding neighborhood, or cross from one side to another either on foot or by car. There is also an underpass at M Street which speeds traffic through but makes the intersection much more pedestrian-unfriendly, and makes the L and O intersections more dangerous because of the cars coming up from the underpass.
Work is already underway to allow turns and cross traffic at O and P streets, next to the ballpark. Alternative 2 would cut through the medians at the other streets as well, and replace the underpass with an at-grade intersection, which would make the area much more inviting.
At the southern end of the Frederick Douglass Bridge, the roadway divides into high-speed freeway-like interchanges which also consume a lot of waterfront land. Both alternatives plan to replace these with something more urban, either a regular intersection (in Alternative 1) or a traffic circle (in Alternative 2). Alternative 2 also creates a traffic oval at the north end of the bridge, at Potomac Avenue. I believe the traffic circles would slow traffic more at these intersections, improving pedestrian and bike safety, but am not entirely sure which is better. The existing circles in DC are fairly unpleasant to walk through or around, since there are so many different entrance and exit roadways with their own walk signals which are usually not coordinated for pedestrians.
One of the best features of Alternative 2 is replacing the cloverleaf interchange between I-295 and Suitland Parkway, which also consume a lot of city land for freeway ramps. Alternative 2 seeks to replace this with an urban diamond, the narrower type of interchange where each ramp runs alongside the freeway and intersects the road in a traffic light. (I’m curious why they don’t recommend a SPUI, which is even better because left turns don’t conflict.)
Both alternatives also have considerable bike, walking, running, and rollerblading infrastructure, widening several bridges and adding space for a “multi-use trail” along the Frederick Douglass bridge and Martin Luther King Jr. Avenue.
Whichever alternative gets built will substantially improve South Capitol Street. The more elements from Alternative 2 make it into the final plan, the better for the neighborhood, and the closer to the L’Enfant vision, the boulevard will be.