Chicago's train company has fired a train operator who dozed off and did not wake up until cars jumped the end of the track at O'Hare International Airport and hurtled up an escalator.
More than 30 people were injured, none seriously, in the crash in March.
The 25-year-old driver, had worked as an operator for two months and reportedly admitted it was not the first time she had dozed off at work.
The Chicago Transit Authority says it will halve the speed limit for trains entering the station to 24km per hour and rejig an emergency braking system beside the track so it is triggered earlier.
The train was travelling at about 42km per hour when it entered the station, at a normal speed, and tripped an emergency braking system beside the track that failed to stop it before the impact, according to the National Transportation Safety Board.