The new general manager of the MBTA is calling for major investment in public transportation as she prepares to take over the nation's most indebted mass transit system.

Beverly Scott, the outgoing chief executive of Atlanta's transit agency, boarded a subway in Boston on Monday and met with riders hit with an average 23 percent fare increase last summer.

Scott, who officially takes over The Massachusetts Bay Transportation Authority on Dec. 17, could not rule out the possibility of fare increases next year. But she promised to work with the agency's board and state legislators on a financial fix.

Scott is leaving an Atlanta system that has also struggled financially.

Massachusetts Transportation Secretary Richard Davey says she made tough decisions — including layoffs — in Georgia and brings fresh perspectives to the MBTA.