In July 2010, Metro took all 4000-series cars out of service following a tragic incident involving a collision on the Washington Metro system. The incident occurred on June 22, 2009, when a train operator failed to stop at a red signal, leading to a rear-end collision with another train on the Red Line near the Fort Totten station. This crash resulted in the deaths of nine people and injuries to dozens more.

The investigation that followed revealed several safety issues, including problems with the 4000-series cars, which were deemed unsafe for operation. As a precautionary measure, Metro decided to remove all 4000-series cars from service in July 2010 to ensure passenger safety while they worked on implementing new safety protocols and upgrading their fleet.

If you would like more detailed information on the incident or the subsequent changes in Metro operations, feel free to ask!