Story highlights Official: No reason, based on schedule, that fatigue should have been a factor

Incident did prompt transit agency to look at train operator scheduling

32 people were injured in last month's incident at the end of Chicago's Blue Line

A union official had said there were "indications" that the train operator "dozed off"

The driver of a train that jumped the tracks last month at Chicago's O'Hare International Airport -- after having reportedly "dozed off" -- has been fired, a transit authority spokeswoman said Friday.

The early morning incident at one of the nation's busiest airports was the operator's second serious safety violation, according to Chicago Transit Authority spokeswoman Tammy Chase. That said, Chase said the woman was primarily terminated because of the severity of that crash, which injured 32 people.

The development came the same day the transit authority announced several policy changes aimed at enhancing safety.

They include requirements that train operators not be working at least one day in a seven-day period and must have at least 10 hours off between shifts (up from the previous 8-hour mandate). Train operators also can't work more than 12 hours (including layover times and non-driving duties) in a 14-hour period.

Photos: Photos: Chicago train derailment Photos: Photos: Chicago train derailment Chicago train derailment – A commuter train car lies halfway up an escalator at Chicago's O'Hare International Airport station after derailing early Monday, March 24. More than 30 people were hurt, according to Chicago police, but the injuries weren't considered to be life-threatening. Hide Caption 1 of 6 Photos: Photos: Chicago train derailment Chicago train derailment – A police officer stands near the derailed train. The Chicago Transit Authority's Blue Line service was suspended between the O'Hare airport and the Rosemont stop after the derailment, a CNN affiliate reported. Hide Caption 2 of 6 Photos: Photos: Chicago train derailment Chicago train derailment – Chicago Transit Authority employees work the scene of the derailment. Hide Caption 3 of 6 Photos: Photos: Chicago train derailment Chicago train derailment – A derailed train car rests on an escalator at the O'Hare station. Hide Caption 4 of 6 Photos: Photos: Chicago train derailment Chicago train derailment – Chicago police said the derailment happened at 2:52 a.m. CT (3:52 a.m. ET). Investigators didn't immediately know what caused the train to derail. Hide Caption 5 of 6 Photos: Photos: Chicago train derailment Chicago train derailment – Passengers board a shuttle bus at the O'Hare station after Monday's derailment. Hide Caption 6 of 6

JUST WATCHED Train derails, slams into platform Replay More Videos ... MUST WATCH Train derails, slams into platform 00:51

Fresh restrictions were also placed on those in their first year of operating trains: They can't do so more than 32 hours a week, though these employees can "work other rail-related duties besides operating trains in their other work hours," the transit authority said in its statement Friday.

These revised guidelines are "nearly identical" to those used by other transit agencies, according to Chase.

She said "nothing about the operator's work schedule suggests that fatigue should have played a factor in her performance."

The driver had a day off four days before the incident, hadn't worked for 18 hours before coming to work that day and worked 55.7 hours in the seven previous days (less than 44 of those as a rail operator), according to the transit authority spokeswoman.

That said, Chase acknowledged, "The O'Hare incident prompted us to take a closer look at our scheduling."

The wreck occurred at 2:52 a.m. on March 24, when an eight-car train failed to stop at the end of the Blue Line when it arrived at the airport station, a Chicago fire official said. The lead car appeared to have climbed an escalator adjacent to the passenger platform.

"I've investigated many accidents and trains do different things," National Transportation Safety Board investigator Tim DePaepe said of the train climbing the escalator. "It's all about kinetic force. I have not seen an accident like this, personally."

A union official told reporters last month that the train's driver may have fallen asleep, CNN affiliate WLS reported

"There are indications that she dozed off, yes," Amalgamated Transit Union Local 308 President Robert Kelly said, according to WLS.