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A police officer stands near a Chicago Transit Authority train car that derailed at the O'Hare Airport station early Monday, March 24, 2014, in Chicago. More than 30 people were injured after the eight-car train plowed across a platform and scaled an escalator at the underground station. (AP Photo/Andrew A. Nelles) ( Chicago Train Derailment )

A derailed Chicago Transit Authority train car rests on an escalator at the O'Hare Airport station early Monday, March 24, 2014, in Chicago. More than 30 people were injured after the eight-car train plowed across a platform and scaled the escalator at the underground station. (AP Photo/Andrew A. Nelles) ( Chicago Train Derailment )

Chicago Transit Authority President Forrest Claypool (C) and National Transportation Safety Board investigator Timothy DePaepe (R) walk up to the microphones to speak to reporters outside of the O'Hare International Airport station where a commuter train derailed on March 24, 2014 in Chicago, Illinois. More than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. The CTA's O'Hare station will be closed while the NTSB investigates the crash. (Photo by Brian Kersey/Getty Images) ( 480769863BK016 )

National Transportation Safety Board investigator Timothy DePaepe speaks to reporters outside of the O'Hare International Airport station where a commuter train derailed on March 24, 2014 in Chicago, Illinois. More than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. The Chicago Transit Authority's O'Hare station will be closed while the NTSB investigates the crash. (Photo by Brian Kersey/Getty Images) ( 480769863BK013 )

A Chicago Transit Authority worker puts up a sign informing travelers that the CTA's O'Hare International Airport station is closed after a commuter train derailed, closing the station on March 24, 2014 in Chicago, Illinois. CTA riders will uses shuttle service to get to and from the airport until the wreckage is cleared after more than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. (Photo by Brian Kersey/Getty Images) ( 480769863BK010 )

Chicago Transit Authority worker Shawanda Bedford (R) directs James Leung away from the O'Hare International Airport station after a commuter train derailed, closing the station on March 24, 2014 in Chicago, Illinois. CTA riders will uses shuttle service to get to and from the airport until the wreckage is cleared after more than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. (Photo by Brian Kersey/Getty Images) ( 480769863BK004 )

Chicago Transit Authority workers erect a tarp to cover the scene where commuter train derailed at the O'Hare International Airport station on March 24, 2014 in Chicago, Illinois. More than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. (Photo by Brian Kersey/Getty Images) ( 480769863BK002 )

A derailed Chicago Transit Authority train car rests on an escalator at the O'Hare Airport station early Monday, March 24, 2014, in Chicago. More than 30 people were injured after the eight-car train plowed across a platform and scaled the escalator at the underground station. (AP Photo/Andrew A. Nelles) ( Chicago Train Derailment )

National Transportation Safety Board investigator Timothy DePaepe speaks to reporters outside of the O'Hare International Airport station where a commuter train derailed on March 24, 2014 in Chicago, Illinois. More than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. The Chicago Transit Authority's O'Hare station will be closed while the NTSB investigates the crash. (Photo by Brian Kersey/Getty Images) ( 480769863BK011 )

Chicago Transit Authority workers put up signs informing travelers that the CTA's O'Hare International Airport station is closed after a commuter train derailed, closing the station on March 24, 2014 in Chicago, Illinois. CTA riders will uses shuttle service to get to and from the airport until the wreckage is cleared after more than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. (Photo by Brian Kersey/Getty Images) ( 480769863BK009 )

Chicago Transit Authority workers stand at the scene where commuter train derailed at the O'Hare International Airport station on March 24, 2014 in Chicago, Illinois. More than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. (Photo by Brian Kersey/Getty Images) ( 480769863BK007 )

Chicago Transit Authority workers direct travelers at the CTA's O'Hare International Airport station to where they can board shuttle busses after a commuter train derailed, closing the station on March 24, 2014 in Chicago, Illinois. CTA riders will uses shuttle service to get to and from the airport until the wreckage is cleared after more than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. (Photo by Brian Kersey/Getty Images) ( 480769863BK005 )

A police officer stands near a Chicago Transit Authority train car that derailed at the O'Hare Airport station early Monday, March 24, 2014, in Chicago. More than 30 people were injured after the eight-car train plowed across a platform and scaled an escalator at the underground station. (AP Photo/Andrew A. Nelles) ( APTOPIX Chicago Train Derailment )

Chicago Transit Authority workers stand outside the O'Hare International Airport station where a commuter train derailed at on March 24, 2014 in Chicago, Illinois. More than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. (Photo by Brian Kersey/Getty Images) ( 480769863BK003 )

Chicago Transit Authority workers erect a tarp to cover the scene where commuter train derailed at the O'Hare International Airport station on March 24, 2014 in Chicago, Illinois. More than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. (Photo by Brian Kersey/Getty Images) ( 480769863BK001 )

Chicago Police work the scene where a Chicago Transit Authority derailed at the O'Hare Airport station early Monday, March 24, 2014, in Chicago. More than 30 people were injured after the eight-car train plowed across a platform and scaled an escalator at the underground station. (AP Photo/Andrew A. Nelles) ( Chicago Train Derailment )

Passengers board a shuttle bus at O'Hare Airport after a Chicago Transit Authority train car derailed at the O'Hare Airport station early Monday, March 24, 2014, in Chicago. More than 30 people were injured after the eight-car train plowed across a platform and scaled an escalator at the underground station. (AP Photo/Andrew A. Nelles) ( Chicago Train Derailment )

A sign informs travelers at the Chicago Transit Authority's O'Hare International Airport station of travel disruptions after a commuter train derailed, closing the station on March 24, 2014 in Chicago, Illinois. CTA riders will uses shuttle service to get to and from the airport until the wreckage is cleared after more than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. (Photo by Brian Kersey/Getty Images) ( 480769863BK006 )

Chicago Transit Authority employees work the scene where a Chicago Transit Authority derailed at the O'Hare Airport station early Monday, March 24, 2014, in Chicago. More than 30 people were injured after the eight-car train plowed across a platform and scaled an escalator at the underground station. (AP Photo/Andrew A. Nelles) ( Chicago Train Derailment )

A derailed Chicago Transit Authority train car rests on an escalator at the O'Hare Airport station early Monday, March 24, 2014, in Chicago. More than 30 people were injured after the eight-car train plowed across a platform and scaled the escalator at the underground station. (AP Photo/Andrew A. Nelles) ( APTOPIX Chicago Train Derailment )

A Chicago Transit Authority workers directs a traveler at the CTA's O'Hare International Airport station to where they can board shuttle busses after a commuter train derailed, closing the station on March 24, 2014 in Chicago, Illinois. CTA riders will uses shuttle service to get to and from the airport until the wreckage is cleared after more than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. (Photo by Brian Kersey/Getty Images) ( 480769863BK008 )

National Transportation Safety Board investigator Timothy DePaepe speaks to reporters outside of the O'Hare International Airport station where a commuter train derailed on March 24, 2014 in Chicago, Illinois. More than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. The Chicago Transit Authority's O'Hare station will be closed while the NTSB investigates the crash. (Photo by Brian Kersey/Getty Images) ( 480769863BK012 )

MARCH 24: Travelers and commuters board shuttle busses at the Chicago Transit Authority's Rosemont station heading to O'Hare International Airport after a train derailment shut down the CTA's station at the airport on March 24, 2014 in Chicago, Illinois. More than 30 were injured when a train, arriving at O'Hare, slammed into the platform overnight coming to rest on an escalator. Airport patrons and workers who use the CTA's Blue Line must take shuttle busses between the Rosemont station and O'Hare while National Transportation Safety Board investigators determine the cause of the crash. (Photo by Brian Kersey/Getty Images) ( 480769863BK020 )

Chicago Transit Authority President Forrest Claypool (C) and National Transportation Safety Board investigator Timothy DePaepe (L) speak to reporters outside of the O'Hare International Airport station where a commuter train derailed on March 24, 2014 in Chicago, Illinois. More than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. The CTA's O'Hare station will be closed while the NTSB investigates the crash. (Photo by Brian Kersey/Getty Images) ( 480769863BK014 )

Travelers board shuttle busses at O'Hare International Airport bus terminal after a commuter train serving the airport derailed at the O'Hare station on March 24, 2014 in Chicago, Illinois. More than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. The Chicago Transit Authority's O'Hare station will be closed while the National Transportation Safety Board investigates the crash. (Photo by Brian Kersey/Getty Images) ( 480769863BK017 )

Travelers board shuttle busses at O'Hare International Airport bus terminal after a commuter train serving the airport derailed at the O'Hare station on March 24, 2014 in Chicago, Illinois. More than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. The Chicago Transit Authority's O'Hare station will be closed while the National Transportation Safety Board investigates the crash. (Photo by Brian Kersey/Getty Images) ( 480769863BK018 )

Chicago Transit Authority President Forrest Claypool speaks to reporters outside of the O'Hare International Airport station where a commuter train derailed on March 24, 2014 in Chicago, Illinois. More than 30 were injured when the train slammed into the platform overnight coming to rest on an escalator. The CTA's O'Hare station will be closed while the NTSB investigates the crash. (Photo by Brian Kersey/Getty Images) ( 480769863BK015 )

Travelers and commuters arrive at the Chicago Transit Authority's Rosemont station and head towards shuttle busses after a train derailment shut down the CTA's O'Hare International Airport station on March 24, 2014 in Chicago, Illinois. More than 30 were injured when a train, arriving at O'Hare, slammed into the platform overnight coming to rest on an escalator. Airport patrons and workers who use the CTA's Blue Line must take shuttle busses between the Rosemont station and O'Hare while National Transportation Safety Board investigators determine the cause of the crash. (Photo by Brian Kersey/Getty Images) ( 480769863BK021 )

Travelers and commuters arrive at the Chicago Transit Authority's Rosemont station on shuttle busses after a train derailment shut down the CTA's O'Hare International Airport station on March 24, 2014 in Chicago, Illinois. More than 30 were injured when a train, arriving at O'Hare, slammed into the platform overnight coming to rest on an escalator. Airport patrons and workers who use the CTA's Blue Line must take shuttle busses between the Rosemont station and O'Hare while National Transportation Safety Board investigators determine the cause of the crash. (Photo by Brian Kersey/Getty Images) ( 480769863BK023 )

Travelers and commuters arrive at the Chicago Transit Authority's Rosemont station on shuttle busses after a train derailment shut down the CTA's O'Hare International Airport station on March 24, 2014 in Chicago, Illinois. More than 30 were injured when a train, arriving at O'Hare, slammed into the platform overnight coming to rest on an escalator. Airport patrons and workers who use the CTA's Blue Line must take shuttle busses between the Rosemont station and O'Hare while National Transportation Safety Board investigators determine the cause of the crash. (Photo by Brian Kersey/Getty Images) ( 480769863BK024 )

Travelers and commuters wait for a train at the Chicago Transit Authority's Rosemont station after a train derailment shut down the CTA's O'Hare International Airport station on March 24, 2014 in Chicago, Illinois. More than 30 were injured when a train, arriving at O'Hare, slammed into the platform overnight coming to rest on an escalator. Airport patrons and workers who use the CTA's Blue Line must take shuttle busses between the Rosemont station and O'Hare while National Transportation Safety Board investigators determine the cause of the crash. (Photo by Brian Kersey/Getty Images) ( 480769863BK022 )

Travelers and commuters arrive at the Chicago Transit Authority's Rosemont station on shuttle busses after a train derailment shut down the CTA's O'Hare International Airport station on March 24, 2014 in Chicago, Illinois. More than 30 were injured when a train, arriving at O'Hare, slammed into the platform overnight coming to rest on an escalator. Airport patrons and workers who use the CTA's Blue Line must take shuttle busses between the Rosemont station and O'Hare while National Transportation Safety Board investigators determine the cause of the crash. (Photo by Brian Kersey/Getty Images) ( 480769863BK019 )