The head of the agency running New York City's bus and subway service has resigned amid a leadership shift at the Metropolitan Transportation Authority.

Howard Roberts was named president of New York City Transit -- overseeing the bus and subway system that carries over 7 million daily riders -- by ex-MTA CEO Eliot Sander. Sander's replacement Jay H. Walder took office last month.

Walder said in a statement Wednesday that Roberts worked hard to lead the agency for the past 2{ years and thanked him for his service.

Roberts will leave the job at the end of the month. Walder says he'll name a replacement soon.