Transit officials in western Pennsylvania say a rear door lock failure sent a woman tumbling from a moving bus in Pittsburgh last week, seriously injuring her.
Port Authority of Allegheny County spokesman Jim Ritchie said "a lock mechanism in the doorway" clearly failed, and officials are trying to find out why that happened.
He said the authority has checked all of the roughly 700 buses in the fleet and found no similar problems, although alignment problems on two doorways were fixed.
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The woman, who fell from the bus as it rounded a corner at about 6 p.m. Friday, remains in the intensive care unit at UPMC Mercy.
The doors are typically controlled by the driver, but Ritchie says the mechanism appears to be at fault rather than "some outside intervention."