CHICAGO (CBS) -- Human error is to blame for the CTA Blue Line train derailment Wednesday night that sent one woman to the hospital, the CTA Workers Union says.
The union is blaming the operator's inexperience and a particularly difficult stretch of track for the derailment.
A 39-year-old woman was hopsitalized with a back injury after the train ended up crisscrossed over the tracks between Rosemont and O'Hare.
A total of 73 passengers were evacuated from the train and led back through the tunnel with luggage in tow.
CBS 2 has learned the rapid transit operator at the controls appears to have made a mistake and then overcorrected, and the CTA Workers Union said that's because he's only been on the job about five years and not always full time.
"A lack of experience leads to accidents like this, just like the 2014 incident," said Kenneth Franklin, Local 308 president.
In 2014 the Blue Line train jumped the tracks and smashed into an escalator at the end of the terminal at O'Hare. The operator said she fell asleep.
After a year-long investigation, the National Transportation Safety Board said, in part, that "the CTA did not effectively manage the operator's work schedule to mitigate the risk of fatigue."
That time more than 30 people on the train were injured, and the crash caused more than $9 million in damages.
"The train hit so hard the doors shattered," one rider said of Wednesday's incident.
The derailment was minor, but railroad operations and safety expert Richard Beall said this type of "crossover" area can be difficult to navigate even for an experienced operator.
Derailments in this area can be difficult to recover from.
"It's pretty rough because you're bouncing over cross ties instead of over smooth rail," Beall said. "You're doing everything to get it stopped in as short a distance as possible."
Now the CTA Workers Union is calling on the CTA to ramp up the training requirements for new rapid transit operators in the interest of safety.
"When you put a full-time job in someone's hands, you're paying them a full-time wage that brings about more knowledge and responsibility," Franklin said.
The Union also says there appears to have been some miscommunication with the control tower.
The CTA released the following statement regarding the derailment:
"Incidents like last night's are rare. CTA has one of the strongest safety records among large U.S. transit agencies.
CTA continues to investigate the incident, and is interviewing all personnel involved. Until the investigation is complete, CTA will not speculate as to the cause.
The derailment was a relatively minor one. The train was traveling 5 mph or less when the derailment occurred.
There is no indication that infrastructure or equipment played any role in the incident. All tracks and signals in the area are functioning properly.
CTA operators receive extensive training. The operator in yesterday's incident has three years of experience, and has no prior safety violations. His training and certifications are current."
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