WASHINGTON (Reuters] – Nearly half of Washington’s 500 railroad operators failed recertification on Sunday. The system will take some out of service. It will also temporarily suspend some trains.

Metro, which serves Washington DC and areas of Virginia and Maryland, will take out service to 72 train operators that were not in compliance with the Metro’s rules before May 20,21. This will temporarily reduce the service of Green and Yellow lines from every 15 to every 20 minutes.

In October, a safety committee ordered that the subway remove 60% of its train cars after inspections following a derailment. While the subway system works to restore train car use and add more, it has maintained a lower schedule.