Prince William County supervisors approved a road project this week that will alleviate congestion outside Quantico Marine Corps base.

County transportation officials said that with the unanimous approval from supervisors, they can begin a $6 million project to widen and realign Fuller Road, which provides access to the base.

Fuller Road is a four-lane, undivided thoroughfare that becomes two lanes just outside the base. The plan is to make it a four-lane divided roadway with a raised median all the way from Route 1 to the check station at the base. The Marine Corps base approved the project in 2009 and it is being supported by federal funds and proffer money, county officials said.

County officials said they hope to begin construction in spring and that it will take about a year to complete.

Construction along Route 1 leading into the base is underway. County officials bought and tore down 40 buildings to turn Route 1 into a six-lane divided highway with a walking trail. The Route 1 construction is expected to be finished in spring 2012.