The National Transportation Safety Board says an unmanned "ghost train" involved in a Blue Line crash which injured more than 30 riders Monday, blew through five emergency mechanisms designed to stop it.
At each one, the train temporarily stopped, then started up again, because "the master lever on the operator console had been left in a setting that allowed the brakes to recover and reset from the emergency brake application."
NTSB investigators have determined that the train managed to travel almost a mile downhill before reaching the Harlem station, where it collided with an outbound Blue Line train, injuring 33 people.
In an emergency Safety Recommendation issued Friday, the Safety Board said they have learned unoccupied CTA trains are "routinely" left powered-up while they are stored, with a brake setting that would allow movement thru the train stop mechanisms. The Chicago rail agency disputed that finding.
"The CTA does not routinely leave out of service trains powered up," CTA spokesman Brian Steele said. "The incident we saw on Monday is very much an aberration."
Among the NTSB's recommendations, that the power out-of-service trains should be cut, with brakes left in a position to ensure that the trains can't move on their own.
"Everything that the NTSB suggested the CTA do, we've already done," said Steele, noting that the agency sent out their own bulletin to staffers last night outlining new procedures.
The NTSB also suggested the CTA begin employing "chocks" to block the wheels of trains left out-of-service, or even derails, which would knock the wheels off the tracks if the trains unexpectedly started moving.
In the emergency bulletin, signed by acting NTSB Chairman Deborah Hersman, investigators stressed they have not yet determined the actual cause of Monday's accident.
But they said the safety issue outlined Friday "needs to be addressed expeditiously to prevent a recurrence."