A series of rail cars that Norfolk Southern recently put into service have been discovered to have defective, loose wheels. "The company said they "immediately notified" the NTSB and the Federal Railroad Administration (FRA) once they found the issue "and began inspecting other cars from this series on our network" which led them to discover additional cases of "unusual wheel movement. Today, AAR through its committee structure took expeditious action and has issued an advisory to stop cars with these wheels from use and interchange until those wheel sets can be replaced,\" the spokesperson said