Sixteen people were hurt when the train hit a snowplow on the tracks last November.
According to National Transportation Safety Board records reviewed by the I-Team, the trainman's blood alcohol concentration was found to be 0.06. That is three times higher than the federal limit for rail employees in safety-sensitive positions.
A second test done on the train operator's blood came in at 0.04, which is also over the federal limit.
An attorney representing six of the victims said, "there are many questions regarding the reaction time of the train's operator as well as his ability to stop the train that could have avoided these injuries."
The NTSB also commented, saying "the investigation is ongoing, however, at this time investigators have not found that the operator's actions contributed to the accident."
The CTA has directed all questions about the investigation to federal regulators, but said the Yellow Line operator "remains out of service."