The derailment of a Light Rail Transit vehicle in the Downtown subway Friday night was caused by the vehicle passing a red "stop" signal and crossing a track switch that was not in the proper position, Port Authority said Monday.
Spokesman Jim Ritchie said it had not been determined whether the vehicle operator was at fault. The agency was continuing to review recorded communications between the South Hills Village Rail Center and the vehicle, along with the onboard data recorder.
"The vehicle went through a signal and entered a switch that hadn't fully moved over to a locked position," he said. "Does that mean it's operator error? The answer is not necessarily."
Nine passengers were aboard when the outbound vehicle derailed between the Gateway and Wood Street stations shortly before 9 p.m. Friday. One person was taken to a hospital with minor neck and back injuries and two others with minor injuries declined treatment at the scene.
The authority was doing maintenance at the time of the derailment and running inbound and outbound service on a single track. During such operations, vehicles are directed by personnel at the rail center as to when they are cleared to cross from one track to the other.
Typically, they would wait until the signal changed from red. But there are situations when a vehicle might be directed to proceed through a red signal, Mr. Ritchie said.
The incident forced the authority to terminate service at Steel Plaza and use bus shuttles to take passengers to Wood Street, Gateway, North Side and Allegheny for the rest of the weekend. Full operations were restored in time for Monday morning's start of service, Mr. Ritchie said.
The unidentified operator is on paid leave pending the outcome of an investigation.
Jon Schmitz: email@example.com or 412-263-1868.