The San Diego Trolley is a light rail system operating in the metropolitan area of San Diego. It is known colloquially as The Trolley. The Trolley's operator, San Diego Trolley, Inc. (SDTI), is a subsidiary of the San Diego Metropolitan Transit System (MTS). The Trolley began service on July 26, 1981, making it the oldest of the "second generation" light rail systems in the United States. The entire Trolley network serves 53 stations, and comprises 53.5mi of route, and three primary lines named the Blue Line, the Orange Line, and the Green Line, as well as a supplementary heritage streetcar downtown circulator known as the Silver Line that operates on select weekdays, weekends and holidays. In Q4 2014, the Trolley was the 4th most-ridden light rail system in the United States, with an average of 119,800 riders per weekday.The San Diego Trolley is operated by MTS, which is one of the oldest transit systems in Southern California dating back to the 1880s. Although its operating names have changed over the years, the two modes of transportation, buses and trolleys, have remained consistent over most of the past 125 years.San Diego Trolley initially used the same German-built Siemens–Duewag U2 vehicles as the Edmonton Light Rail Transit system in Edmonton and the C-Train in Calgary, Alberta, Canada, and the Frankfurt U-Bahn in Frankfurt, Germany. The fleet has since been expanded to include Siemens SD-100 vehicles, and most recently Siemens S70 vehicles.
