San Diego's Metropolitan Transit System (MTS) awarded Siemens Mobility a contract for 25 S700 Low-floor Light Rail Vehicles. The cars will operate the entire 53-mile double-tracked MTS light rail network, including on the 11-mile Mid-Coast Trolley extension, which is scheduled to open in 2021. It will extend San Diego's current Blue Line from the heart of downtown north to University of California San Diego and University Town Center.

The new vehicles will replace Siemens Mobility's high-floor SD100 LRVs, which were manufactured in the 1990s. This purchase and subsequent purchases will make San Diego's fleet fully low-floor and accessible. Delivery of the new LRVs is expected in 2021.

The S700 cars are the latest advancement of the fully-electric S70 low-floor vehicle platform designed and manufactured by Siemens Mobility at its solar-powered facility in Sacramento, Calif. They are characterized by an open and spacious low-floor interior. The wide aisleway makes the vehicle much easier to traverse into and around for passengers, bicycles, and wheelchairs. There are also energy efficiency features like LED lighting, which not only utilize less energy, but also last longer.

Siemens Mobility's relationship with MTS began in 1980, with an order for 71 cars of their original high-floor U2 model. This was followed by an order in 1993 for 52 SD100 cars. In 2004, with the passengers in mind, the leadership at MTS started transitioning to a low-floor car system with an order for 11 S70 vehicles. The transition was continued five years later with a larger order for 65 S70 cars, followed by another order for 45 S70 vehicles, which are currently being delivered.