The station that will complete Metro's Green Line in Prince George's County is scheduled to open in March 2001, but road improvements needed to ease expected traffic congestion there will still be years from completion, even though officials have had 15 years to prepare.

Interim road improvements are underway at the Branch Avenue Station, the Green Line's terminus and one of five stations now under construction on the line. But those projects will not be enough to guarantee problem-free traffic flow for thousands of commuters who will drive to the station, particularly at rush hour, according to traffic forecasts from the Maryland State Highway Administration.

Although officials have narrowed the options for a long-term fix, no final plan has been selected and no funds set aside for design or construction of the larger project, which is expected to cost about $45 million and take at least four years to complete.

"It's not going to be gridlock [when the station opens], but we are going to experience more traffic and more traffic turns, and that . . . will slow people down," said George Cardwell, special assistant to the county's public works director. "We all acknowledge that we need to do more than what's being done out there now."

County and state officials disagree on why large-scale road improvements have not been made at the station, which is expected to draw 8,130 new Metro riders a day and will offer them 3,263 parking spaces to use.

Prince George's County officials said they had a hard time convincing the state--which shares construction costs with the federal government--that major highway improvements were needed.

Eric Foster, supervisor of transportation planning for Prince George's County, said county officials wanted the state to take action in the early 1990s, when there was still time to make access improvements before the scheduled opening.

"We were very concerned that we would have this large station at the end of the line . . . with 3,000-plus parking spaces and access to the station [only] at at-grade signal lights," Foster said. "The state kept putting us off. It was never a priority."

But Neil J. Pedersen, planning director for the State Highway Administration, said that he was surprised the county blames the state. Although the Metro access project was on a list of transportation priorities submitted by the county, "I don't recall it being number one," Pedersen said.

"I'm not going to dispute that they were saying there was a need, but there are a lot of other needs identified in Prince George's," Pedersen said. "This wasn't at the top of the priority list."

In fact, it is sixth on the most recent list approved by County Executive Wayne K. Curry (D), the County Council and state legislators.

Pedersen agreed that some of the intersections near the Metro station would be at capacity when the station opens. "But it won't be a disaster," he said. He noted that intersections near other Metro stations are very busy.

"Hopefully, we provide enough capacity to prevent total gridlock," he added.

At the moment, the Green Line ends at the Anacostia Station, but it is being extended 6.5 miles, with two new stations in the District and three in Prince George's. Construction, which began in September 1995, is on schedule, Metro officials said this week.

In addition to its 3,263 parking spaces, the Branch Avenue station will have 19 spaces for car-pool commuters, 152 kiss-and-ride spaces and 15 bus bays. It is expected to serve not only Prince George's County residents but also commuters from fast-growing Charles, St. Mary's and Calvert counties.

State Del. Kerry Hill (D-Prince George's) said officials did not anticipate the growth boom in Southern Maryland when the Branch Avenue station was planned.

"By the time [the station] is built and completed, it's going to be overwhelmed from the start," Hill said.

Traffic forecasts by the State Highway Administration indicate that three of the five key intersections leading to the Branch Avenue station will have "extremely heavy congestion" during rush hour when it opens, even with the interim improvements. The worst intersections will be Branch Avenue and Auth Road, and Auth Road and Maryland Route 337.

The state started construction this summer on its portion of the interim project. It is widening a ramp off the Capital Beltway and adding lanes to Auth Road at a total cost of $1 million. The county, which expects to start construction next year on its part, is spending about $2 million to add turn lanes to Auth Road and to widen the road into the station entrance.

Those improvements are scheduled to be completed by the opening of the new station, according to state and county transportation planners. But that is little comfort to residents who live near the new stations and who already deal with congestion during rush hour.

"It seems like they waited until the system was upon us and then started gathering data," said Jesse Reeves, president of the Hillcrest Heights Civic Association. "We are going to be swamped with traffic."

CAPTION: Concrete workers build a curb near the Branch Avenue Metro station, scheduled to open in March 2001. Critics say nearby roads can't handle the expected increase in traffic.