Dallas Read says if the trains start rolling past her house, she's moving out.

For the last 45 years, Read has spent every morning on her back porch on Elm Street in Chevy Chase, soaking in the silence of the morning. Trains rumbling by every six minutes during rush hour would wreck her routine, she said.

But consider Alison Smith's predicament. She lives in downtown Silver Spring and braves the traffic on East West Highway five days a week to get to work in downtown Bethesda. She allows 40 minutes to an hour every morning for the trip, which would take approximately 15 minutes by train -- if one were available.

This clash of interests is a classic example of how the fate of a proposed new suburban transit line plays itself out in a county that has experienced explosive growth in the last 20 years and that doesn't take development blueprints lightly.

At issue is the proposed 4.4-mile light-rail line on the Georgetown Branch Corridor between Bethesda and Silver Spring. The corridor includes the easternmost 3.3 miles of the Georgetown Branch right of way and 1.1 miles along the CSX Metropolitan Branch main line to the Silver Spring station on Colesville Road. The light-rail line is part of a larger proposal that outlines several transit options for the right of way.

The proposed trolley would have three cars to a train, and each car would seat 84 passengers, said Ben Ross of the Action Committee for Transit, a nonprofit citizens group in Montgomery County. The trolley would run every six minutes during peak hours and carry 19,500 people every day, according to the most recent study pub lished by the Maryland Mass Transit Administration. A one-way trip would take approximately nine minutes. It has not been decided whether the state of Maryland or Metro would operate the trolley, Ross said.

Supporters of the trolley say it would relieve congestion on major roadways, benefit the economic viability of both downtown Bethesda and Silver Spring and help meet clean air standards set in the 1990 Clean Air Act Amendments.

"This is a unique opportunity for the county," said Ross. "It benefits the residential and the commercial communities, it doesn't generate traffic and it won't harm the environment."

But the proposal has drawn opposition from Bethesda and Chevy Chase homeowners who say the trolley is too costly, too noisy and just downright unnecessary.

"The impact on downtown Bethesda and Chevy Chase would be devastating," said Rosemary Berger, secretary of the Bethesda Coalition, an umbrella association for civic and neighborhood commissions. "Those who live on the right of way will see the value of their property go down. Downtown Bethesda will get more development. And Bethesda can't afford any more of that."

The Georgetown Branch line follows an old CSX railroad spur that carried coal trains from Silver Spring to a federally owned power plant in Georgetown from 1915 to 1985. Montgomery County bought the abandoned railroad line in 1988, and since then has been looking to use the right of way as a link between Bethesda and Silver Spring across Rock Creek Park, and as a connection between the two arms of the U-shaped Red Line.

The Maryland Mass Transit Administration is close to completing an environmental impact study to determine whether the trolley's design meets environmental standards. Once that is proven, the county can apply for federal funding.

The trolley would cost up to $205 million to build and $4.2 million a year to operate, although opponents of the trolley line say that figure is conservative.

The federal government could pay 80 percent of the construction costs, while the remaining 20 percent, or $40 million, would be shared between the state of Maryland and Montgomery County. According to Ross, the county paid a large portion of its 10 percent share when it paid $10 million in 1988 to buy the right of way.

The state most likely will draw from the Maryland Department of Transportation trust fund set up by motor vehicle taxes and fees, according to Anthony Brown, spokesperson for the Maryland Mass Transit Administration.

These costs include extending the Capital Crescent Trail, which presently runs between Bethesda and Georgetown. That is because the county purchased the right of way under the Rails and Trails Act, which encourages recreational construction in urban areas by requiring buyers of abandoned railroad tracks to use them for parks or trails.

The trail, which would run alongside the tracks, has a group of influential supporters who are neutral on the light-rail proposal as long as it does not negatively impact the integrity of the trail. But they have voiced some concern as to whether the light-rail line will run on two separate tracks. Maryland transportation authorities said only sections of the Georgetown Branch line would be double-tracked.

"If the county installs two one-way tracks in certain sections, there may not be enough room for the trail in parts of the right of way that are very narrow," said Henri Bartholomot, a board member of the Coalition for the Capital Crescent Trail.

Trolley opponents welcome the construction of a hiker-biker trail. Read, whose back yard would face the trolley tracks were the light-rail proposal to pass, said that extending the Capital Crescent Trail would allow her to keep the 60-foot-tall trees that shield her home from the noise and clutter of Montgomery Avenue, which runs parallel to her street.

"I feel very strongly that the 4 1/2 miles of trees that separate our neighborhood from surrounding commercial development are our only protection," Read said. "The trees would be torn down and replaced by nothing but ugliness and noise."

Read has filed suit against the county, along with 11 other Chevy Chase residents. They cite a law that grants ownership through adverse possession, which states that a person can become the legal owner of a piece of property simply by using it for a long period of time.

The plaintiffs claim that they have been using part of the right of way, approximately 10 feet, for over 20 years, and that the county would be infringing on private property were it to take that land for the construction of the trolley.

In the meantime, another lawsuit is pending, filed by the Columbia Country Club in Chevy Chase.

The proposed line would run through the club's golf course. The country club is arguing, under adverse possession law, that it owns the 1,800-foot right of way.

The club is trying to prevent the county from building on the course, saying it would interrupt golf games and disturb the quiet on the greens.

"We have been opposed to this {trolley line} from the very start," said Vincent Burke, a Columbia Country Club board member. "It is a waste of the taxpayers' money, and we plan to fight it until this issue is resolved." CAPTION: Dallas Read, a resident of Chevy Chase, is among a group of residents suing Montgomery County to stop it from building a trolley line on this right of way behind her house.