The Washington Metropolitan Area Transit Authority announced they will return a dozen 7000-series railcars to service next week.

WMATA announced the additions will bring the total number of 7000-series railcars – WMATA’s most recent line of trains – in operation to 20 after WMATA was granted permission to run up to eight trains in June. The reintroduction process comes after WMATA pulled all of its 7000-series trains from service after a Blue Line derailment last October.

“Our 7000-series trains are the newest and most reliable in Metro’s fleet, and they are key to providing the level of service our customers want and deserve,” Randy Clarke, WMATA’s general manager and chief executive officer, said in a release Friday.

The additional railcars will run on the Red Line after previously having only been allowed to run on the Green and Yellow lines, according to WMATA’s September return to service plan. WMATA hasn’t said when 7000-series trains will return to the Blue, Orange and Silver lines, which service the Foggy Bottom station.

WMATA will announce new schedules for all six of its lines sometime this week, which will reflect the increase in operating railcars.