In March 2013 photo, traffic flows onto inbound 11th Street Bridge from I-295N, on left, and D.C. 295S, on right. (Photo courtesy of 11th Street Bridge project.)

This is likely to be the biggest traffic improvement of early 2014 for the D.C. area’s commuters: On Friday, the District Department of Transportation plans to open a third lane to handle traffic coming from the 11th Street Bridge onto the Southeast-Southwest Freeway.

11th Street Bridge DDOT image shows new traffic pattern toward downtown D.C.

Traffic officials and managers of the bridge project attribute much of the morning congestion in the bridge’s inbound span to the lack of this third lane. While many phases of the bridge project have been completed, the extra lane coming off the inbound span has been unavailable because of highway construction on the Navy Yard/Capitol Hill side of the Anacostia River.

“The completion of the third lane is a major milestone for this project,” DDOT Director Terry Bellamy said in a statement Wednesday. “This adds 50 percent more capacity, which will help with some of the delays that motorists have been experiencing for the last several months.”

The bridge and its adjacent freeways are part of a major east-west commuter route, and the third lane won’t cure all ills along the way. But it will do this: Many drivers coming onto the inbound span no longer will need to weave among the lanes to line up for the Southeast-Southwest Freeway. The slowdown on the inbound span because of this weaving is a significant source of the traffic backup that ripples back onto Interstate 295 to the south and D.C. 295 to the north.

Despite the opening of three new spans and many new ramps during the past several years, the 11th Street Bridge remains a work in progress. When this new traffic connection is in place, crews will begin demolition of the old highway structure by the Navy Yard. Drivers heading for Eighth Street SE, the Barracks Row area, will be detoured to M Street SE, then to 11th Street SE to I (Eye) Street SE.

Thursday night detour
To set up the new traffic pattern, DDOT plans to close the westbound Interstate 695 ramp to M Street from 10 p.m. Thursday to 5 a.m. Friday. Drivers will be detoured to the I-295/D.C. 295 exit ramps to 11th Street SE so they can reach M Street SE and the Navy Yard area via the local span of the 11th Street Bridge.