Drivers on the 16th Street Bridge and underneath it on Military Road NW already have seen plenty of off-peak construction work preparing for replacement of the bridge, but the project soon will affect rush hour traffic.

The District Department of Transportation plans to begin lane closings on the bridge on March 27. This will start with a lane closing on the northbound side, but will eventually affect southbound traffic as well. These full-time lane closings for the bridge reconstruction are likely to be in effect for about four months.

Lanes on Military Road also will be closed, but the main effect is likely to be felt on 16th Street, a major north-south commuter route with limited alternatives for cars and Metrobuses.

Paul Hoffman, DDOT project manager. (Robert Thomson - The Washington Post) Paul Hoffman, DDOT project manager. (Robert Thomson – The Washington Post)

D.C. Mayor Muriel Bowser and DDOT director Leif Dormsjo plan to highlight this upcoming phase of the project during a visit to the bridge Monday morning. If this is your commuting route and you haven’t worked out an alternative already, now is the time. Don’t wait till the lane reductions start. Congestion is likely to be extremely bad, especially in the early days when some drivers, unfortunately, will first learn of the project.

But District officials have been warning for many months that this phase was approaching. The construction impact is likely to be so severe that I included the project on my top 10 list of transportation developments that would affect commuters in 2015.

Other effects: The 16th Street ramp to westbound Military Road NW will be closed during this phase, DDOT said. A detour will be posted. Drivers also should watch for turn restrictions at the 16th Street bridge.

Military Road underneath the bridge will be completely closed for up to eight weekends to dismantle parts of the old structure. Drivers may find their access to bridge ramps blocked, with detours set up.

The traffic congestion is likely to be less on Military Road than on 16th Street, but the Military commuters should still allow extra time for their trips.

Travel tips

The location of the bridge limits the alternative routes. Rock Creek Park is just to the west. “There are not a lot of options,” Paul Hoffman, the DDOT project manager, pointed out to me during a tour of the bridge area last fall.

DDOT hopes to divert 8,000 vehicles a day from the work zone. The primary north-south option is Georgia Avenue, to the east of the bridge. Some drivers will envision other options that involve the park or neighborhood streets, but they are likely to be frustrated by narrow, winding roads and intersections that were not meant to handle many commuters.

Allow extra travel time if your Metrobus goes through the work zone. (Robert Thomson - The Washington Post) Allow extra travel time if your Metrobus goes through the work zone. (Robert Thomson – The Washington Post)

“Georgia Avenue was made to move a lot of traffic,” Hoffman said. DDOT plans to adjust the traffic signals to compensate for additional volume. But Georgia Avenue already is slow at rush hours through such neighborhoods as Silver Spring, Petworth and Shaw.

One popular commuting option for drivers in the Silver Spring area combines Piney Branch Road and 13th Street NW, but this route doesn’t have the traffic capacity that Georgia does.

Drivers who now find 16th convenient don’t need to use Georgia for the entire trip. South of the work zone, the major links between the two roadways are Arkansas and Colorado avenues.

Capital Beltway commuters who use the Georgia exit in the morning will be better off sticking with southbound Georgia rather than making the right onto 16th.

DDOT officials say that replacing the bridge is absolutely necessary. The stalactites beneath the structure are a sign of the deterioration. (Ricky Carioti – The Washington Post)

This project is going to have a major effect on the Metrobus S Line on 16th Street. But one alternative for commuters in the Silver Spring area is to take the Metro Extra 79 bus, the limited-stop service on Georgia and Seventh Street NW.

Some commuters who normally drive downtown may find it more convenient to park at one of the outer Red Line stations — Glenmont, Wheaton, Forest Glen or Silver Spring — and ride downtown.

While the planners’ major concern is with traffic on 16th, some long-distance commuters from the north who use Missouri Avenue and Military may find they’re better off on East West Highway in Montgomery County, even though that route gets crowded at peak periods.

The blocks around the work zone are residential. Give the locals a break. If you get stuck in traffic on 16th, don’t block the intersections and bottle up the neighborhoods.