The Municipal Transportation Agency plans to buy up to 260 new light-rail cars to replace and expand its Muni Metro fleet of 151 cars. If the Board of Supervisors approves the contract, Siemens Corp. would build the S200 light-rail vehicles, which have three different exterior designs, in Sacramento. A prototype car would arrive by the end of 2016 with the first 24 cars delivered in 2018, in time for the Central Subway opening.