 Another feature was the return of cast steel trucks, which were previously only used on the Rohr cars.This was done as a cost-saving measure, since fabricated trucks take additional time to manufacture due to the machining required.The National Transportation Safety Board began an investigation about service life of these cars due to non-revenue service derailments in Metrorail yards and the January 7, 2007, derailment of a revenue train on the Green Line at the station.