Bangkok SkyTrain operator BTS Group has signed a THB2bn ($67m) contract with Siemens to supply 35 additional cars in order to expand its fleet of 35 three-car trains in Bangkok, Thailand.

The rail operator said the carriages will meet the expected growth in ridership on the Sukhumvit route following the opening of the On Nut-Baring extension in August 2011.

The cars will be delivered over the next 30 months, according to the Bangkok Post .

With the four-car trains, BTS expects the ridership on the Sukhumvit line to increase by 500,000 passengers a day from next year.