The SD-100 and SD-160 are light rail vehicles (LRV) that were manufactured by Siemens Mobility between 1992 and 2013 for the North American market. The vehicles were all constructed at the Siemens facility in Florin, California. The primary difference between the models is that the older SD-100 uses direct current motors, while the newer SD-160 uses alternating current motors. Both models were built with a "high-floor" design and could be equipped for level boarding at high-platform stations or with steps and wheelchair lifts for passenger loading at street level. This model was manufactured and marketed alongside the Siemens SD-400 and SD-460 LRV, which offered both level boarding at high-platform stations and steps for passenger loading at street level. This model has been replaced by the Siemens S700 and S70, a low-floor LRV for passenger loading at street level and the Siemens S200, a high-floor LRV for level boarding at high-platform stations. History Production of the SD-100 was launched in 1992 when the Regional Transportation District, located in Denver, Colorado placed an order for 49 vehicles. The physical design was derived from the U2A car that was built between 1985 and 1991, but built with more modern mechanical equipment. The first vehicles rolled off the production line at the Siemens facility in Florin, California in 1994, in time for the start of Light Rail service in Denver. In 1993, the San Diego Metropolitan Transit System ordered 52 SD-100 cars as the San Diego Trolley system was expanded with a new line, these entered service in 1995. as of 2021 they are currently being phased out and replaced by Siemens S700. The final order for the SD-100 came in 1996, when the Utah Transit Authority, located in Salt Lake City placed an order for 23 vehicles that were delivered before the start of the TRAX light rail service in 1999. In 2001, Siemens launched the SD-160 light rail vehicle, which used alternating current motors instead of direct current motors and outward sliding doors. Calgary Transit ordered 72 vehicles for its CTrain service, while the Utah Transit Authority ordered 17 vehicles as it expanded the TRAX light rail service. Deliveries to both agencies started in 2003. The physical design of the SD-160 was updated in 2005 with a new end cap that changed the look of the front/rear of the train. The Edmonton Transit Service ordered 57 of the redesigned SD-160 vehicles and