[This post has been updated]

Are drivers finding the commute along Interstate 395 more difficult now that federal employees are shifting to Alexandria’s Mark Center? One driver wonders where all the extra traffic is.

Dear Dr. Gridlock:

I live in Fairlington and drive south on Interstate 395 past the gargantuan Mark Center. There had been predictions of bumper-to-bumper gridlock after the building opened.

But the southbound traffic hasn’t changed at all. Where is the additional traffic everyone said would come?

— David Kaplan, Fairlington

The move into the Mark Center by 6,400 federal employees didn’t occur all at once. In fact, it’s still going on. The Federal Highway Administration and the governments of Virginia and Alexandria have taken some steps to ease the traffic flow.

But do other drivers agree that traffic hasn’t lived up to the dire forecasts made by people like me? I predicted this area, where heavily traveled I-395 and Seminary Road come together, would become even more of a problem than it had been starting last fall. (I wonder if drivers heading north to work will report a different experience. That’s what traffic engineers seem most concerned about.)

The governments say they’re not done making fixes.

One week from tonight, the Virginia Department of Transportation plans to hold a public hearing on the preliminary design for an $80 million HOV/transit ramp at I-395 and Seminary Road. The Jan. 25 hearing is scheduled for 7 to 9 p.m. at Francis C. Hammond Middle School, 4646 Seminary Rd., Alexandria.

A traffic report done last fall by the Virginia Department of Transportation did find problems. For example, traffic using the ramp from northbound I-395 to Seminary Road sometimes backed up onto the Interstate during the morning rush. That ramp was also a problem during the afternoon peak, as was the southbound ramp from Seminary Road to I-395.

Seminary Road had very heavy traffic, especially around North Beauregard Street.

Virginia took some steps to ease the congestion on northbound I-395. Traffic signals were retimed, new signs were installed and the I-395/Seminary Road interchange rotary was restriped to allow two left turn lanes for traffic headed to the Mark Center. The route from the ramp to the Mark Center was reconfigured to allow two lanes of traffic.

Meanwhile, transit agencies increased their bus service.

VDOT plans to make further changes this year and beyond. Those include:

* Intersection and turn lane modifications at Beauregard Street and Seminary Road, estimated for completion in September.

* Turn-lane expansion at the Mark Center Drive and Seminary Road, also scheduled for completion in September.

* Construction of a pedestrian bridge from Southern Towers over Seminary Road to the Mark Center, estimated for completion in December 2013

* Expansion of the ramp from Seminary Road to southbound I-395, with an estimated completion in 2015 or 2016.

Many commuters think that’s the reverse of the right order. The traffic improvements should have come before the transfer of the workers to the Mark Center. A lot of this work will need to go on while people are trying to deal with already crowded traffic conditions.

UPDATE: Anne Hughes, press secretary for Rep. James P. Moran (D-Va.), pointed out to me this afternoon that an extra provision to limit traffic is now in effect. Moran and other members of the local delegation were able to add a Mark Center parking cap into the Omnibus Appropriations Bill signed into law on Dec. 23.

The parking cap will limit the number of usable spaces to roughly 2,000 until the Department of Defense can demonstrate for 90 consecutive days that traffic lanes in the area are not at failing levels of service.