High Quality Content by WIKIPEDIA articles! The Southeastern Pennsylvania Transportation Authority (SEPTA) is a regional municipal authority that operates various forms of public transit ? bus, subway and elevated rail, regional rail, light rail, and electric trolley bus ? that serve 3.8 million people in and around Philadelphia, Pennsylvania. SEPTA also manages construction projects that repair, replace, and expand infrastructure and rolling stock. SEPTA serves the combined city and county of Philadelphia, Delaware County, Montgomery County, Bucks County, and Chester County. SEPTA also serves New Castle County in Delaware, and Mercer County in New Jersey. SEPTA has the 6th-largest U.S. transit system by ridership, with about 306.9 million annual unlinked trips.