 The following diagram depicts an eight-car train, with couplers represented by crosses and semi-permanent link bars represented by dashes.The 7000-series cars are so technologically advanced as to render them incompatible with the existing fleet.Presented with that issue, Metro's board members recognized the seriousness of the decision, but former Metro general manager John B. Catoe indicated that the board needed to decide "in months" on whether to go ahead with the rail car order, regardless of whether or not the Dulles extension was approved.