Philadelphia is home to one of the largest trolley / light rail systems in the United States, operated by the Southeastern Pennsylvania Transportation Authority (SEPTA).  The system is made up of eleven lines, eight in the city and three in the western suburbs.  The city trolley routes include the five Subway-Surface lines, which serve Center City, West, and Southwest Philadelphia, and the three surface-only routes (suspended since 1992), which serve primarily North Philadelphia.  The city routes were all formerly operated by the Philadelphia Transportation Company (PTC).  The suburban trolley routes include the Media and Sharon Hill lines and the Norristown High Speed Line (P&W).  The suburban routes were formerly operated by the Philadelphia Suburban Transportation Company (Red Arrow Lines).