The National Transportation Safety Board is issuing urgent safety recommendations in response to the crash on Metro in June that killed nine people.
In it's investigation, the NTSB found that track circuits were sending out random signals that confused the system that is supposed to keep trains apart. The NTSB said it was so concerned about the malfunction that the agency is asking the Federal Transit Administration to warn all metro and rail operators using similar systems across the country.
A series of specific safety recommendations have been given to Metro and the circuit manufacturer Alstom Signaling, whose circuits have failed in previous incidents.
Sabri Ben-Achour reports...