The Transportation Planning Board added construction of a proposed east-west highway between Montgomery and Prince George's counties to its long-range plans yesterday, moving the region's first new highway in a generation a significant step closer to being built.

The decision, backed by more than two-thirds of the board, ends nearly a year of fitful debate that centered on whether the highway is affordable, whether it would ease traffic and add jobs, and whether mass transit would be more sensible. Those lines of argument were pursued again yesterday during more than an hour of public testimony and another hour-plus of panel discussion.

Backers of the road, called the intercounty connector, said it was well past time to move forward on a project that has been debated for four decades. They said it would take cars off secondary roads and bring development to the region.

"Once again, people must take time out of their busy lives to come here today to tell you to do something that is obviously needed," said Tom Reinheimer, a connector supporter from Boyds. "The time is now to quit playing games with the lives of people stuck in traffic."

The proposed eight-lane toll road would run 18 miles between Interstate 95 in Prince George's and Interstate 270 in Montgomery. Supporters have said it is needed to connect Maryland's biggest business community with the Baltimore-Washington International Airport and the busy I-95 corridor.

State officials, who said they plan bus service along the road, also predict that it would relieve some traffic on secondary roads, although they have backed off from claims that it would alleviate Capital Beltway congestion.

The connector was one of several road projects -- including the widening of Route 4 and Route 202 in Maryland and of Interstate 66 and Route 50 in Virginia -- added to the body's long-range plans. The designation means they are consistent with the region's transportation planning vision and that they have satisfied air quality and financing requirements. Maryland officials plan to borrow as much as $1 billion against future federal funds and use state money to pay for the road.

"This is a big hurdle for advocates of the project to get over," said Ron Kirby, transportation planning director for the Metropolitan Washington Council of Governments. "If they meet all the local impact [requirements], they can build this project."

The next step for the connector is consideration of the environmental impact statement, which state officials said would be released this month.

Yesterday's approval came over the opposition of many speakers and a handful of board members, who said a decision should have been delayed until after the environmental impact statement is made public. They also argued that a decision couldn't be made because the project's costs were unclear. Maryland officials announced this month that the road's price tag has risen from $1.7 billion to as much as $2.1 billion.

Opponents said the project would drain the state's transportation resources and damage the environment. They also argued that it would not solve any traffic problems, largely because it would spur suburban sprawl and create a greater reliance on cars.

"We're paving over the region, polluting all over the place," said Rodney Roberts, a Greenbelt City Council member and board representative. "We have a big problem, but the car is not the answer to it."

After the vote, proponents said it would be a boon to everyone who gets behind a wheel. "We're thrilled," said Bob Grow of the Greater Washington Board of Trade. "This is a victory for the traveling public in terms of getting where you need to go in a quicker, safer, more cost-effective manner."