A passenger train that slammed through its end-of-the-line barrier at Chicago's O'Hare International Airport this week tripped an automatic emergency stop system and was not speeding when it entered the station, a federal investigator said on Tuesday.
The crash sent the Chicago Transit Authority train hurtling onto an escalator and stairs at the airport's mass transit station early on Monday. Thirty-two people sustained injuries that were not life-threatening.
Investigators hope to interview the train operator on Tuesday afternoon and have not reached any conclusions about the cause of the crash, Ted Turpin, an investigator with the National Transportation Safety Board, told reporters.
A union official on Monday said he spoke to the operator after the crash and believed she may have dozed off. The train operator, who has not been identified, told the union she had been working very long hours and had indicated to him she was extremely tired.
Turpin said the train was traveling at a normal speed of 25 to 26 miles per hour (40-42 kph) when it entered the station and triggered a physical device beside the track that put it into emergency mode.
"It was attempting to stop the train, brakes were applied," he said.
The NTSB hopes to release the train on Tuesday to the CTA, which will be responsible for clearing the tracks, Turpin said. It may have to cut up the front car resting on the escalator, but may be able to pull a second car back, he said.
Turpin said he hoped it would take "a lot less than" a week to restore service at the station. Buses are shuttling riders between O'Hare and the next train station.
The investigation includes a review of station video of the train arriving and an outward-facing video recorder on the train, as well as signals and the train's condition. The crash happened at about 3 a.m. CDT (0800 GMT) on Monday.
The incident was the second in recent months involving an apparently out-of-control CTA train. In September, an unmanned CTA train ran loose onto active tracks and collided with a standing train at a suburban Chicago station during morning rush hour, injuring at least 33 people.