The board appointed Dorval R. Carter Jr. this week.
He's the CTA's executive vice president for operations support and will temporarily take over daily responsibilities for managing Chicago's public transportation system.
Mayor Richard Daley will decide on a successor.
Carter started his legal career with CTA and has held numerous positions with the agency for seven years, including general attorney for corporate law.
He also spent a decade at the Federal Transit Administration.
Carter says he's honored to be chosen. He says he plans to work collaboratively with the board through transition.