Wheels on Metro rail cars involved in derailment had failed repeatedly, NTSB says

The transit system’s 6000 sequence, which makes up about 15 p.c of Metro’s automobiles, has been sidelined since November, when the company pulled the trains out of service after two practice separations on the Purple Line over practically two months. Metro found that a few of the equipment that joins the automobiles was restored with the flawed components or instruments, and it has only recently been returning a handful of the 184 automobiles to service.