The Pentagon has agreed to provide hundreds of millions of dollars for traffic improvements in Bethesda and Fairfax County to help alleviate congestion caused by the move of Defense Department employees under the base realignment and closure program.

The Department of Defense will provide $180 million to widen Route 1 at Fort Belvoir, funding a key state project to help accommodate an influx of employees being transferred, U.S. Rep. Jim Moran (D-Va.) said Tuesday.

The width of Route 1 at Fort Belvoir would be increased from four to six lanes. Virginia, which has spent $400 million on BRAC improvements, sought federal help for the widening project.

The Defense Department also will provide $88.9 million for intersection, lane improvements and an underpass that will connect the National Institutes of Health with the Walter Reed National Military Medical Center in Bethesda, U.S. Rep. Chris Van Hollen (D-Md..) said.

“This money — which has taken nearly two years to secure — will help ensure wounded warriors and their families are able to access the new facility and lessen the impact on the surrounding community,” he said.

The colors were lowered at Walter Reed Army Medical Center in the District in July and the last patients were moved in August.

According to Virginia officials, the stretch of Route 1 that accesses Fort Belvoir carries 56,000 vehicles each day and “has one of the highest highway crash rates in Northern Virginia.”

The widening project, which will affect 3.5 miles of Route 1, could begin in 2013, state officials said. They estimated it would take up to three years to complete.

“Every day, commuters are stuck in long traffic queues on Route 1 that has only worsened with the additional traffic generated by BRAC changes bringing more defense personnel to Fort Belvoir,” Gov. Robert F. McDonnell said in a statement. “This widening will improve the quality of life for thousands of commuters and visitors.”

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