Fairfax County's clogged roads are doing more harm than just making people late for work, a new report found.

Traffic is so heavy that it's forcing the county to buy more school buses just to get students to school on time, the Private Sector Energy Task Force found.

"More school buses mean fewer teachers or higher costs," the report said.

And county officials worry that gridlock is prompting employers to pull up stakes and head for Maryland.

The task force noted that Guernsey Office Products had to build a second distribution center in Maryland because bridges across the Potomac are so congested.

"I think there is an economic development issue here that is driving business out of Virginia," said Jim Corcoran of the Fairfax County Chamber of Commerce. "Our lack of additional strategy on the roads is costing jobs."

Transportation is Fairfax County's third-largest category of energy use -- meaning unclogging roads is the No. 1 priority for county leaders eager to go green, the report said.

Highway improvements are a must, according to the task force. Even with more residents expected to travel by train when Metro's Silver Line opens, people will still be driving cars, and even buses rely on the road network.

"This report calls congestion the low-hanging fruit in improving energy efficiency and in cleaning the environment," said AAA Mid-Atlantic's Lon Anderson, a task force member. "I hope that the county leadership will look at this and say, 'Yes, we need to devote far more resources to congestion mitigation.' "

Anderson said congestion in Fairfax is hurting the whole county, not just drivers.

"Not only does it bug everybody and not only does it cost us all money, but congestion really is a tax," Anderson said. "It's a tax on everybody that lives in our region, where we have the worst congestion in the United States. In Virginia, which is so adverse to taxes, this is a tax that has grown and grown and grown."

The task force will pass its findings on to the county board.