For the past two years, friends and foes of the proposed Rosecroft Metrorail line have battled over the course of Metro in southern Prince George's County.

Three times, opponents of the Rosecroft line have taken their case to the County Council trying to have plans for it scrapped. Three times they have failed.

Last January, they even tried to enlist Gov. Harry R. Hughes in their ranks. They were unsuccessful because the governor decided to leave the final decision in local hands.

A plan approved in 1968 by the Metro Board called for construction of a rail line along Branch Avenue. However, the Prince George's County Council voted in 1978 to support an alternate alignment to terminate at Rosecroft Raceway.

Since then, in the face of pressure from supporters of both lines, the County Council has twice reaffirmed its decision to support the Rosecroft alignment over Branch Avenue. Moreover, the Maryland Department of Transportation and the Metro Board since have given the green light to the Rosecroft line.

But even in the face of these political and administrative defeats, advocates of the Branch Avenue line have fought on. Supported by a group known as Citizens for the Branch Avenue Metro, Rosecroft opponents now have entered a new and perhaps final phase of the struggle, seeking to mount a legal assault on the proposed line.

The first volley was fired a month ago when the owners of Brinkley House Apartments and Bill Cairns Pontiac, located just off Branch Avenue, filed suit in U.S. District Court claiming their business would be damaged by plans to substitute the Rosecroft line for the Branch Avenue line. A hearing is scheduled next month.

About two weeks ago, a group of citizens in the predominantly black community of Hillcrest Heights filed a civil rights complaint with the U.S. Department of Transportation, claiming that the building of the Rosecroft line would do substantial economic and environmental damage to their community.

According to residents, the Rosecroft Metro would run within a 100 feet of about 50 Hillcrest Heights homes, bringing noise pollution and destroying community open space.

A spokesman for the group of about 200 Hillcrest Heights citizens said that if their efforts to block construction fail, they will take the Metro Board and the county to court.

Other citizens in the area also are weighing court actions against the Metro board, including leaders of St. Barnabas Church. Under the present plan, the Rosecroft line would run through church property.

"I think the people in the southern part of the county really deserve mass transit services, but the line should be where the people are," said State Delegate Lorraine Sheehan, coordinator of Citizens for the Branch Avenue Metro.

Sheehan's group, backed by developers in the Branch Avenue area, has sought in the past year to pressure the County Council into reversing its 1978 decision in support of the Rosecroft alignment. The group argues that Metro and the county would save money and increase ridership in the long run with a Branch Avenue line.

While a Metro report compiled last July shows that construction of the Rosecroft route would cost $113 million and the Branch Avenue line $144 million, Sheehan's group believes that $10 million would be saved yearly in operating expenses if the Branch Avenue line were built.

However, there is widespread disagreement on the numbers. Proponents of both lines are quick to hand out fat packets of statistics supporting their cases.

Rosecroft supporters argue that the long-term development potential of the area surrounding the Rosecroft Raceway make it a good investment risk for the future. Their opponents to the north, like Sheehan, argue that the decision on the alignment should be made on the basis of what is, now what may be in the future.

Realizing the millions of dollars in business may be at stake with the decision on where Metro is located, powerful economic interests have chosen sides in the Branch Avenue vs. Rosecroft fight. For example, the district court suit filed last month has attracted several Rosecroft area developers as co-defendants, including the owners of Rosecroft Raceway.

Both sides aruge that a decision not to build their line would damage them economically. They say past investment decisions have been based on an assumption -- grounded in some fact -- that Metro would pass their way.

Over the past year, a new issue has surfaced -- that of the environmental impact of the Rosecroft route. Opponents say that building it would bring noise and traffic congestion to communities like Hillcrest Heights, hurting the quality of life and property values in them.

"We'd like the Department of Transportation to cut off funds for the project because this line does more damage to our community that it has done to any in metropolitan Washington," said Ronald Hill, a resident of Hillcrest Heights and attorney for about 200 other residents who oppose the Rosecroft line.

Hill said that if the transportation department does not cut off funds for the line, his group may go to court.

Sheehan said her group would back the Hillcrest Heights residents if they decide to go to court.

"I don't think anybody really cared about the residents of Hillcrest Heights when they made the decision to accept the Rosecraft alignment," she said. "The Branch Avenue line would not have disrupted any communities. Now the people in Hillcrest Heights are going to have trains whizzing by their windows."

With the talk of lawsuits filling the air, some county leaders have begun to wonder whether court delays will jeopardize the future of a southern Prince George's rail route.

"You know, we would end up with nothing," said County Council Chairman Parris Glendening. "Virginia already seems to be rushing to make sure all of its lines are built. It we get wrapped up in court for years, Virginia might finish all of its lines, then ask itself why it should contribute to the completion of the other routes.

"After the court fighting ended, southern Prince George's could be left with no Metro route at all," added Glendening.

Suggestions in the opposite direction have not moved the Branch Avenue Metro advocates.

"We've heard promises that both routes could be built, but you have to wonder just how feasible that is. If there is a second route built, it's going to be a hell of a long way down the line, if ever," said Sheehan.

"Up until 1978, there was never any serious talk of a Rosecroft Metro being built first. Why should it now get priority over a Branch Avenue line?" she added.

The suit filed last month is scheduled to be heard in U.S. District Court in Baltimore in mid-July. Because other suits may be filed in the future, no one knows when Metro will begin work on the line that will run through Anacostia to southern Prince George's County.