The Alexandria City Council approved spending $600,000 on an express bus service between the King Street Metro station and Mark Center, site of new offices for about 6,400 Defense Department workers, as long as the Pentagon agrees to reimburse the city for its expense. Under the proposed reimbursement agreement, the Defense Department would pay not only for the bus rehabilitation, but the $500,000 annual operating costs. In exchange, Pentagon personnel would ride for free on the entire DASH bus system, including the expanded service along the AT2 route between King Street and Mark Center. Vice Mayor Kerry Donley said the city expects to have a deal in principal with the Pentagon by Jan. 19, though defense officials say it will take longer to get the necessary signatures.

The measure is one of several aimed at easing traffic congestion expected at the Mark Center site at the intersection of Seminary Road and Interstate 395, with more costly highway improvements, such as new turn lanes and traffic patterns to allow easier access to the site, still being discussed.

There also are plans to run more shuttles from Metro stations at Franconia, Pentagon and West Falls Church stations, said Paul McMahon, director of the BRAC Program Office, which oversees the Army's move to the Mark Center. The King Street shuttle will also provide service to Amtrak and Virginia Railway Express riders. McMahon said Pentagon officials will negotiate with the city each year to continue payments and service of the express buses.

"At least right now, we have no end state in mind," he said. "Obviously, we'll be monitoring how the ridership goes and where are the proper places to be providing services from."

Alexandria officials estimate that each bus running between Metro and Mark Center would take between 15 and 17 cars off the road.

Four surplus DASH buses, now unusable, will be rehabilitated and put back into service at a cost of about $150,000 per bus. Each bus will have all its main systems replaced, and will receive a new paint job to distinguish it as an express bus. New buses would cost about $650,000 each.

Alexandria officials said the buses should be ready by early August, when the first of the Pentagon workers arrives at the Mark Center.

While defense workers can ride the express buses for free, Alexandria residents would pay normal fares, creating a new source of revenue for the city.