Revenue service
Twenty-four new Type 9 Green Line cars were delivered between 2017 and 2020. Revenue service began in late 2018 and all 24 cars were planned to enter service by the fall of 2019, although actual acceptance continued through 2021. The Type 9 cars will provide additional rolling stock to allow for Green Line Extension operations, and will not replace any of the existing fleet. The cars were made by CAF USA, Inc., with the shells and frames made in Spain, and final assembly and testing done at their plant in Elmira, New York. , the first unit had been expected to enter passenger service in Spring 2018, with all 24 cars in service by the end of the year. The first Type 9 car, #3900, began revenue service on December 21, 2018.