Under the proposal, two lanes would be added to I-270 in each direction between Interstate 370 and Frederick, while U.S. 15 in Frederick would be widened one northbound and one southbound lane.

Kirby said the plan envisions a project that would be financed through conventional transportation revenues, with the traditional 80 percent federal and 20 percent state split of the costs. Unlike some proposals for the project, the plan the board will vote on doesn't depend on toll financing, he said. He said the state could pay for the project by extending the completion time to 2030.

The I-270 corridor in Montgomery and Frederick counties is plagued by some of the  worst traffic jams in Maryland. Many local officials there are pushing for the road to be widened as a way of relieving the congestion.

But Ben Ross, president of ACT, said the project would waste money that could better be used for transit projects that would take  cars  off the roads. He said that when the stretch of I-270 south of Shady Grove was widened, the new lanes quickly filled up and became as congested as they were before.

"It's just going to dump more cars into Montgomery County and  tie up all the roads in Montgomery County," he said.

Ross' group is supporting what it calls an "all-transit" alternative that includes MARC improvements and the extension  of the Metro Red Line to Germantown.

Maryland Transportation Secretary Beverly Swaim-Staley said the board has to include the project in its  plan so that the state's environmental study of the corridor's needs can continue. She said that study includes the Corridor Cities Transitway, a proposed light rail or rapid bus line between Shady Grove and Clarksburg in northern Montgomery.

Swaim-Staley said the transit project is the state's priority and that  it can later be separated from the proposed highway widening.  She insisted that the project's inclusion in the Washington-area plan does not commit the  state to building it.

The project would have little direct impact on Baltimore or its nearby suburbs because it involves a commuting corridor used  mostly by Washington-area residents  and workers. But the cost of the project is enormous, as are the potential environmental effects. It is not something the state can undertake without having an impact on its entire transportation program. Baltimore-area policy makers would be well-advised to stay on top of the debate over a project that has the potential to becomes as controversial as the Intercounty Connector.