An attorney for William Rockefeller, the engineer at the helm of the Metro-North train that derailed Sunday in the Bronx, said that his client experienced highway hypnosis before the incident.

Highway hypnosis is a phenomenon that occurs when a driver loses track of time and begins to zone out while behind the wheel. Rockefeller admitted to his union representation that he was nodding before the crash that killed four people.

Dr. Michael Canders, of Farmingdale State College, says highway hypnosis is not exclusive to drivers on the road or engineers on the rails. He says pilots can also experience the phenomenon while flying airplanes.

Canders says highway hypnosis is difficult to practice against or prepare for in a simulator. He says all drivers can combat zoning out by getting enough sleep.

"The sameness of that task allows the mind to wander to other tasks," said Canders. "[Drivers] may be thinking about something completely different."

The NTSB is still looking into what the engineer was doing after his Saturday shift and before his Sunday shift.

According to the Federal Railroad Administration, a train crew member is not allowed to be on duty unless he or she has had at least eight consecutive hours off duty over a 24-hour period.