The option takes the total number of vehicles on order to 215, making it Siemens' largest-ever order for light rail vehicles in the United States.

The mock-up was publically unveiled by SFMTA director of transit Mr John Haley, San Francisco Mayor Mr Ed Lee and Siemens infrastructure and cities USA president Mr Michael Cahill and displays design features adopted following a public consultation last year. These include a new seating configuration, new interior colour scheme and new exterior styling.

SFMTA signed a $US 648m contract with Siemens last year for 175 SF200s, and the first prototype vehicle will be delivered in December 2016 with a further 23 units due to arrive by 2018. The LRVs will be assembled at Siemens' Sacramento plant in California.

SFMTA has one remaining option in the contract for a further 45 vehicles.