NTSB investigators spoke with the woman for two hours on Wednesday. During that time, she told them she fell asleep when pulling into the O'Hare station early Monday morning.
"She did admit that she dozed off prior to entering the station and did not awake again until the train hit close to the end of the bumper," NTSB lead investigator Ted Turpin said. "She woke up when she hit."
Her hand must have kept pressure on the power handle to keep the train moving forward.
"She didn't really remember, but she made an assumption she must have or the train would have stopped," Turpin said. He said the driver was "very cooperative and very forthcoming" about the derailment. She also told officials that in February she had another experience where she dozed off and overrode a station. CTA officials became aware of the situation and admonished her at that time.
Officials will now take a look at her work cycle, and see what she does on her time off, Turpin said. She has about 60 days experience running trains.
Still to review- video from 41 surveillance cameras; information gathered on the automatic emergency braking system that activated, but didn't stop the train; and the track and train equipment.
Officials said they have finished their onsite investigation and will now allow the CTA to start removing the train.
"We're still looking at all the numbers on that. It's hard to analyze all of that," Turpin said.
Turpin said NTSB will now return to its offices and review all the information.
The wreck cost $6 million in damage just to the track and equipment alone. The CTA said it hopes to have the station opened by the weekend.
The train's driver is currently on injured on-duty status. She could be discharged, but the CTA does not plan to take any actions until the investigation is complete.
CTA Blue Line derailment video posted online
Blue Line derailment video posted to YouTube shows the moment of impact from what appears to be a surveillance camera at the O'Hare station.
The train careens past the end of the track and up onto an escalator at the O'Hare International Airport early Monday morning. A security guard and a man who had just come up that escalator are seen running out of the way.
Thirty-two people, including the train's driver, were hurt. None of the injuries was serious.
"It's a very jarring picture. And, that said, I think the most important thing to be said on the subject was thank God no one was seriously injured," Chicago Mayor Rahm Emanuel said.
The video was posted on YouTube overnight for a few hours, but then taken down. There are more than 40 surveillance cameras at the CTA's Blue Line O'Hare station. Officials have not officially said the video came from one of those cameras.
On Tuesday, NTSB officials said the train was going 25 or 26 miles per hour when it pulled into the O'Hare station early Monday morning. That is a normal speed for entrance, NTSB lead investigator Ted Turpin said of the preliminary review. What isn't clear is how fast the train was going when it derailed at the end of the platform and why an automatic emergency braking system didn't stop it.
Turpin said that system went into action on the tracks as the train traveled toward the platform, but failed to stop it.
"It activated, whether it did it in time or not, that's an analysis we'll have to figure out," Turpin said.
The NTSB is removing recording devices from the wreckage, which includes a head-on camera from the front of the train. Those videos were to be sent to NTSB experts in Washington, D.C.
On Tuesday, investigators also said they spoke with the train's driver for about two hour. They would not comment on what came out of that interview.
On Monday, CTA union officials said the woman may have "dozed off" at the controls.