Northern Virginia leaders are divided over whether to install express lanes or Metrorail along Interstate 66 outside the Capital Beltway as the state studies solutions for the highway's notorious stop-and-go traffic.

Express lanes have the full support of Fairfax County Supervisor Pat Herrity and the tacit approval of the state's top roads official, Secretary of Transportation Sean Connaughton. But two prominent members of Congress -- Democratic Reps. Jim Moran and Gerry Connolly -- are calling for a rail extension to Centreville.

Herrity says express lanes would be faster and cheaper to build, and could offer speedy new bus service that would move large groups of people as Metro does. The lanes would offer congestion-free rides to those willing to pay a toll, similar to the express lanes on the Virginia side of the Beltway.

"We need a solution today, not a solution for four years from today or 20 years from today," Herrity said. "I think there is an understanding among the governments in the region that rail is a very expensive solution."

Herrity says he knows of at least three private companies that are considering joining the commonwealth in a public-private partnership to build the express lanes if the state OKs them.

But Connolly and Moran have a bill in Congress to study extending Metro to Centreville along the highway.

"Northern Virginia is home to the worst traffic in the nation. To reduce the number of cars on the road, and in turn lower the amount of pollutants and greenhouse gases in our air, we need to improve our transportation infrastructure," Moran said. "This includes expanding Metro, upgrading bridges and roadways, and investing in smart public transit systems."

There may be room for compromise between those pushing for Metro and those set on express lanes.

"Extending the Orange Line seems like the most natural option since the right of way already exists, but there may be other alternatives to consider," Connolly said.

And Herrity said the express lanes could be built in such a way that Metro could be installed in the middle of the highway at a later date, as the Orange Line is currently.

Virginia finished a study last month on how to fix traffic on the highway. The Commonwealth Transportation Board will decide later this year which of the proposed options -- express lanes, more regular lanes, extending Metrorail, extending Virginia Railway Express, buses, doing nothing or other actions -- to push forward for further study.