The Washington Metropolitan Area Transit Authority returned eight 7000-series trains to circulation Thursday after the carts were out of service for over 200 days following a Metro line’s derailment last year.

WMATA pulled all of its 7000-series railcars – the most modern of Metro’s fleet – in October after a derailment near the Blue Line’s Arlington Cemetery stop caused a broad safety investigation into the trains, a move which resulted in 60 percent of Metro’s total fleet being removed. WMATA officials said in a release that Metro has been training inspectors since mid-May on new protocols like daily wheel measurements to further reduce the likelihood of future derailments and downtime.

“Metro has been focused on training inspectors on the required safety processes which include daily back-to-back wheel measurements using a digital gauge,” WMATA officials said in a statement. “Metro conducted a number of pre-operational test exercises with inspectors to ensure a smooth launch of the new process.”

The eight 7000-series trains have been initially introduced to the Green and Yellow lines, with officials expecting Metro to have developed a “steady rhythm” of inspections and operations in July, when they hope to reintroduce the trains to the Blue, Orange and Silver lines.