Benefit changes for non-union employees have led more managers than usual to retire from the Southeastern Pennsylvania Transportation Authority.
Some 85 of SEPTA's 1,700 managers are leaving before the changes take effect next year.
Under the changes, overtime will no longer factor in pension payments and managers will have to pay an increasing amount toward their health care coverage.
A new formula also determines who is eligible. New employees must stay 10 years, rather than five, to be eligible.
Deputy general manager Rich Burnfield tells The Philadelphia Inquirer the agency looked at changes that would provide long-term security.
SEPTA pays about $90 million a year into the pension, which has $1.1 billion in asset. Returns have been less than predicted and SEPTA has tried to stabilize pensions.