As it begins its search for a successor to outgoing general manager Carmen E. Turner, Metro's governing board will have to find someone to lead the regional rail and bus agency through what some officials say will be one of the system's most difficult periods.

Federal money to operate Metro continues to decline, and Congress appears ready to trim the federal share of the $2.7 billion cost of building the last 13.5 miles of the planned 103-mile system.

That means the state and local governments that pass the hat to make up the difference will have to pick up more of Metro's costs, and these governments already are hurting. The District has fallen behind in its payments, forcing Metro to borrow money.

Local governments are going to have to come up with hundreds of millions of dollars in the coming years to replace and repair the aging equipment that carries about 1 million passengers a day. Higher fares and delays in service and construction are likely.

"This region will have to decide how it will finance public transportation," said Turner, who is joining the Smithsonian Institution as its chief operating officer. "The region will have to look at the money available for transportation and find the right allocation for those dollars based on some comprehensive regional plan."

Metro has always had challenges but generally has found the right manager at the right time, starting with Jackson Graham, a master builder who put the holes in the ground. Turner, the fourth chief executive, took Metro from an agency that mostly built the system to one that also had to pay more attention to operating the trains and buses.

"Certainly it's going to be a dislocation," said Mary Margaret Whipple, of Arlington, the Metro board chairman. "It's never easy to lose someone good. I'm confident Metro is a strong and able organization and the transition will be smooth."

Given the prestige and visibility of managing the transit system in the nation's capital, officials expect that several people will apply for Turner's job, which now pays $109,000 a year but likely would pay more to attract a new manager. A search committee is expected to be named soon; Turner leaves in mid-December after seven years as Metro manager.

"It won't be an easy or quick task replacing Carmen Turner," said Jack Gilstrap, executive director of the American Public Transit Association. He said that many top managers have contractual obligations that would prevent them from leaving immediately for Metro.

Inside the organization, there are no obvious candidates who have been groomed to succeed Turner. As for the two finalists from 1983 who competed before Turner was chosen, William A. Boleyn is nearing retirement as Metro's finance manager and Theodore Weigle has recently taken a job with Bechtel, the giant international engineering firm. Weigle said he will not seek the post.

Part of Turner's success, especially in unifying Metro's 9,000-member work force, is the symbolic role she provided to women and blacks, some officials said. The Metro board isn't necessarily looking for a member of a minority to replace Turner, board members said, but there are a few in high places in other transit agencies.

Shirley A. DeLibero, who headed Metro's bus operations from 1982 to 1986, became general manager of New Jersey Transit last month. She could not be reached; most of the transit industry is attending its annual convention in Houston, where Turner's resignation caught the industry by surprise.

The operations manager of Seattle's Metro system and two senior officials of the Detroit area's transit agency also are minorities.

"I think someone's sex and race are less important than their personal skills," Whipple said. "Clearly the position is open to all."

Turner said that she did not have someone in mind to replace her, but that she would be involved in finding her successor.

Though Metro's general manager is the top executive in the organization, much of the day-to-day managing is done by seven department heads. This has freed Turner for the important and time-consuming job of dealing with the board, local and state officials, Congress and the Bush administration. The manager, then, is expected to be skilled not only at administration of the Metro bureaucracy but also personal lobbying, at which Turner excelled.

She set a new standard for Metro's dealings with organized labor that her successor will be expected to continue. Under Turner, transit workers agreed to three contracts, all of which were negotiated between Metro management and the transit workers union, avoiding binding arbitration.

"I wouldn't want to turn the clock back to the days before Carmen was manager," said James M. "Tommy" Thomas, president of the local transit workers union, which represents two-thirds of Metro employees.

Whoever succeeds Turner also will take over an agency that is beginning some serious soul-searching about its future role in the region. For example, should the rail system be expanded beyond 103 miles and should light rail connections to Metro be built?

"Metro needs to come to terms with how it views itself with the outside world," said board member Cleatus E. Barnett, of Montgomery County.

Another future worry is maintenance. The rail system is 14 years old; Metrobus was created 17 years ago. Repairs already are being deferred, and Metro estimates it will need more than $600 million over the next five years for capital needs but can cover only one-third of that from existing sources.