William Rockefeller fell asleep at the controls of the Metro-North train that derailed in The Bronx.
The agency has developed new systems for training workers, inspecting tracks and reducing train speeds.
William Rockefeller had an over-the-counter drug in his system that causes drowsiness, a report found.
An NTSB report is expected to show that William Rockefeller suffered from the sleep disorder.
The death of four people is a tragedy but it may not be a crime, sources said.
There was nothing wrong with the brakes on the Metro-North train that crashed near Spuyten Duyvil.
The engineer woke up and tried to hit the brakes to stop the speeding train, sources said.
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