The house near Falls Church where Norma Holmes has lived for 25 years sits at the crossroads of Washington's regional debate over transportation, pitting her leafy neighborhood, its ballfield and modest homes against the needs of thousands of drivers who use the increasingly jammed Capital Beltway.

A block or so from Holmes's front lawn, 220,000 cars shift between Interstate 66 and the Beltway every day on a huge interchange that officials now say needs to be even larger to accommodate a proposed expansion of the Beltway from eight lanes to 10 or 12.

If that happens, Norma Holmes and her neighbors will lose their houses or find themselves living next to towering ramps. If the Beltway doesn't expand, officials say, the region's "main street" will be a parking lot for more than 18 hours a day in another two decades or so. Driver frustration will skyrocket, and business leaders, who are campaigning for better area roads, warn that the region's economy will grind to a halt along with the traffic.

"If we're not careful, we're not going to be talking about rush hour, we're going to be talking about rush day," said Tom Farley, the Virginia Department of Transportation's Northern Virginia District Administrator.

The debate over what to do with the overburdened Beltway, when to do it and how much it will cost is now in full swing on both sides of the Potomac, although Virginia is further along in developing its plans. The expansion Virginia is proposing envisions a Beltway that could be as much as 232 feet wide with car-pool lanes and separate lanes for local and express traffic.

It's an idea that drew hundreds of angry citizens to a series of public meetings last week.

"I'm scared, I'm just downright scared," said Holmes, a retired government worker, after she attended one of three meetings held last week by VDOT officials. "The new configuration is going to put my second story on eye level with [the interchange]."

If approved by state, local and federal officials, Virginia's proposed Beltway widening would begin at the Springfield "Mixing Bowl" (already undergoing a $350 million reconstruction) and end at the American Legion Bridge 13 miles away. It would include 10 interchanges, cost $2 billion, primarily in federal highway money, and all of it would lie in Fairfax County.

The immediate focus of transportation planners is the connection between I-66 -- a major conduit for commuters from as far west as Front Royal -- and the Beltway. That is where VDOT officials say they would begin the construction project about 2004 if it's approved. That interchange is the most unsafe, they say, and it's where traffic bottlenecks the most.

Today, the interchange has six ramps, but under plans being considered, that number would grow to 16, with separate elevated roads carrying local, express and car-pool traffic in all directions. Flyover ramps, which now reach 75 feet in height, could get 25 to 35 feet taller.

The prospect has struck dread among the residents of the Shrevewood neighborhood, where American flags hang from well-tended front porches, basketball hoops adorn garages and some neighbors leave their doors unlocked.

Bob and Nikki McClain say a behemoth Beltway interchange would destroy the quality of life in Shrevewood, where they bought a small house with an acre of land in 1985.

Here back yards blur into a communal area. There is a quarter-mile go-cart track for all the neighborhood children to use, a treehouse, a fort and an informal baseball diamond.

But plans for the new interchange show strands of pavement crisscrossing that land, ballfield and all.

"You go from a wide open neighborhood where you have a park and ballfield next door to living next to one of the largest interchanges in the U.S.," Bob McClain said. "We're mad, and we're sticking together and we're going to fight it."

Regardless of the brewing opposition, the highway engineers designing the wider Beltway and its interchanges say it's necessary to correct past mistakes. There are no ramps, for instance, to take outer-loop Beltway traffic to eastbound I-66, or westbound I-66 traffic onto the Beltway's inner loop.

There also are questions of safety. The current interchange uses a left-entry ramp that merges I-66 traffic onto the Beltway's fast lanes. In addition, ramps are built in tight circles, requiring drivers to slow considerably. The new interchange will have gently sloping ramps that allow cars to travel at up to 45 miles per hour.

"If we are going to redo this, we are going to do it the right way," said Robert McDowell, the vice president for HNTB Inc., the chief engineering firm for the project. "People say this is a lot. [Its size is] what it takes to make it work."

Opposition to the Beltway expansion, and particularly to the interchange, while most vocal in nearby neighborhoods, also includes environmental interests and anti-sprawl activists, who say a wider Beltway will only invite more cars and produce more congestion.

"What we're concerned about is adding capacity to encourage more people to drive," said Roger Diedrich, an official with the Virginia chapter of the Sierra Club. "If they paused, and did a good job at looking at alternatives, they would discover better ways to get the job done. They should stop the runaway planning, look at the alternatives, and see what the community wants."

Diedrich and other critics are also concerned about a deterioration in air quality if there are more cars on the Beltway, and they advocate more study of mass transit -- such as rail -- on the Beltway or parallel to it.

Faced with a similar need to expand the capacity of the Beltway, Maryland officials are considering adding transit lines parallel to the road and putting in car-pool lanes that would be open to toll-paying single drivers.

Much of the opposition to Virginia's plans recently has focused on how the state will assess the impact of its wider Beltway on the neighborhoods and nearby land.

And last week, the 300 Shrevewood residents who attended a VDOT meeting demanded to know why transportation officials are doing an environmental assessment for the project, rather than the more comprehensive environmental impact statement.

VDOT insists that there is no significant difference between the two. But Farley said after the meetings that the department is considering doing the more comprehensive study.

"It's fair to say that in light of the public involvement, we're going to have to rethink this," he said.

For Fairfax politicians, handling constituent opposition to the project could determine their success at the ballot box -- if not this November when the local supervisor and countywide chairman are unopposed, then in the future.

But elected leaders also are fearful of what might happen if they don't address future transportation issues. Supervisor Gerald E. Connolly (D-Providence) has tried to remain objective on the issue. Although he represents residents most affected by the project, he also stands for much of Tysons Corner, where expanding commercial development depends on good transportation.

"My role, as I see it, is to be an advocate for my neighborhoods while also trying to work toward some sort of transportation balance," Connolly said.

Connolly has said he supports an improved interchange at I-66, but he has dodged the issue of whether the Beltway needs to be wider. He's also been critical of VDOT for what he calls "overdesigning" road improvements, making them bigger, costlier and more intrusive than they need to be.

"VDOT has a long way to go toward minimizing the impact on neighborhoods and homes," he said.

And Connolly is quick to point out that the Beltway's congestion is not caused by interstate trucks or Maryland commuters. Officials estimate that 70 percent of the traffic on the Beltway in Fairfax County is generated by its own residents.

"It's shopping trips and day trips. We're the ones who use that Beltway and are basically transiting by car," he said. "We have met our enemy, and it is us."

Virginia's Beltway Expansion

Virginia is preparing to redo seven interchanges on the Beltway as part of widening the region's "main street." The more lanes on the Beltway, however, the larger the interchanges, prompting some residents to worry about their neighborhoods shrinking.

The I-66 Interchange is slated to be among the first to be widened; residents are concerned about their neighborhood.