to nine new trolley stations: Tecolote Road, Clairemont Drive, Balboa Avenue, Nobel Drive, VA Medical Center, UCSD West/Pepper Canyon, UCSD East/Voigt Drive, Executive Drive, and UTC. The northern terminal station, UTC, is part of the UTC Transit Center, at Westfield UTC in the University City/UCSD area. Current service Lines , trolley service operates on three daily lines: the Blue, Green, and Orange Lines, and traveling through 65 total miles of mostly double-track rail and serving 62 stations. A fourth line, the heritage streetcar Silver Line, operates more limited weekday and weekend service, in a clockwise 'circle-loop' around downtown San Diego only. Stations The San Diego Trolley system has 62 operational stations serving its four Trolley lines. Fourteen of the Trolley system's stations operate as transfer stations, which allow passengers to transfer between lines. There is one universal transfer point (i.e. allowing for transfers among all four lines) in the system in downtown San Diego: the 12th & Imperial Transit Center station. The adjacent Santa Fe Depot/America Plaza/Courthouse stations, which are within walking distance of each other, also allow for transfer among the four lines. Six Trolley stations are end-of-line stations. Of the 53 San Diego Trolley stations, 37 stations are within the city limits of San Diego, serving various neighborhoods in San Diego; the other 16 stations are located in the cities of Chula Vista, El Cajon, La Mesa, Lemon Grove, National City, and Santee. Most of the stations in the San Diego Trolley system are 'at-grade' stations. There are 8 aerial stations, mostly on the newer Green Line. There is just one Trolley station in the system that is underground – the SDSU Transit Center station – also on the Green Line. About half of San Diego Trolley stations offer free park and ride lots. Most Trolley stations offer connections to MTS bus lines. Hours of operation The San Diego Trolley's three main lines operate regular service between 5 am and midnight, seven days a week. Limited service on particular segments is provided before 5 am and after midnight. However, there is no rail service between 2 am and 3:30 am. During these hours when there is no passenger service, freight trains of the San Diego and Imperial Valley Railroad operate on the trolley's right of way. Service on the Blue Line operates every 15 minutes, seven days a week, with service every 7.5 minutes during weekday rush-hours; late-night