WTOP has the story on what caused this morning’s major Orange and Blue line delays: a large piece of maintenance equipment derailed near Cheverly. The incident marked the fourth derailment on the Metro system in recent weeks. Two weeks ago, a vacuum maintenance truck derailed twice on the same day along the Orange Line, and later that evening, an empty passenger train derailed at the Mt. Vernon Square/7th Street/Convention Center station. Today’s incident damaged some of the tracks near the Cheverly station, which had to be repaired.