The intersection of Route 1 and Fairfax County Parkway is seen in this file photo. (Gerald Martineau/For The Washington Post)

Northern Virginia officials broke ground Monday on a long-awaited widening project on U.S. Route 1 meant to relieve traffic congestion near the Fort Belvoir military installation.

The 3.5-mile stretch of Route 1 between Mount Vernon Memorial Highway and Telegraph Road experiences some of the region’s worst rush-hour traffic. About 80,000 cars pass through Fort Belvoir’s gates each day.

Officials had been trying to deal with the congestion at Fort Belvoir for nearly 20 years, before federal Base Realignment and Closure (BRAC) actions resulted in even more traffic and a public outcry that prompted Congress to appropriate money for traffic mitigation.

In 2012, the Defense Department released $180 million toward Route 1 improvements.

The result when the project is finished will be six lanes of traffic instead of the current four, with bike lanes and safer crosswalks installed on the sometimes treacherous road, officials said.

The project also will include a 32-foot-wide center median that can be used for express buses and, eventualljy, commuter rail, which officials hope will help lure more economic activity to the area.

“This day has been a long time coming,” said Rep. James P. Moran (D-Va.), who was instrumental in securing $300 ­million in BRAC-related transportation improvements across the country, including what is going toward Route 1. Fairfax County supervisors hope to commemorate that role by renaming that portion of the highway after Moran.

The BRAC plan, announced in 2005, did not account at first for extra traffic problems that would occur after thousands of military employees were transferred to Fort Belvoir, which has limited public transportation service, from areas close to Metrorail and bus stops.

“If BRAC had been a rezoning and somebody had said we’re going to have 20,000 new jobs, and they’re all pretty much coming by automobile, we would still be having the public hearings on how we mitigate the impacts,” said Rep Gerald E. Connolly (D-Va.), who was chairman of the Fairfax County Board of Supervisors when the effort was launched.

“We were left to our own devices to address the impact on the southern part of our county.”

In addition to the Route 1 project, federal officials are preparing to open a new road that will allow commuters to cut through Fort Belvoir from Route 1 to Telegraph Road, which they hope will further ease traffic.

A similar shortcut, Woodlawn Road, was closed for security purposes shortly after the Sept. 11, 2001, terrorist attacks.