The Subway–Surface Trolley Lines are the remnants of an extensive pre-World War II streetcar system, similar to the Boston Green Line and San Francisco Muni Metro. The trolley lines were originally run by different companies, until their consolidation by the Philadelphia Rapid Transit Company in 1906. The trolleys run in a tunnel from the Drexel University and University of Pennsylvania campuses to a loop around City Hall. Unlike light rail systems with articulated vehicles, the trolley lines use vehicles closer in size to classic PCC streetcars.