Engineer on Derailed Train ‘Consciously Asleep’: Is That Possible?

Experts don’t recognize the term, but say episodes of microsleep are potentially dangerous

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Robert Stolarik / AP

Metro-North Railroad engineer William Rockefeller is wheeled away from the area where the commuter train he was operating derailed in the Bronx borough of New York City on Dec. 1, 2013

According to the New York Daily News, investigators said train engineer William Rockefeller Jr. was “consciously asleep” moments before the train he was driving reached 82 m.p.h. (132 km/h) in a 30-m.p.h. (48 km/h) zone when it crashed, killed four people and injured dozens more. Rockefeller told law-enforcement officials he was in a “daze” and didn’t “know what I was thinking about” before he slammed on the brakes to slow the train down.

Sleep experts don’t recognize the term consciously asleep, but say there are transitions from wakefulness to sleep during which different parts of the brain go off-line. During these periods, says Dr. Katherine Sharkey, an assistant professor of medicine and psychiatry and human behavior at Brown University, “wakefulness is very unstable.”

Throughout this transition, the brain may slip in and out of microsleeps, or brief periods that may last only several seconds and brain activity slows enough to indicate sleep. In sleep labs, researchers can measure these occurrences by hooking participants up to an electroencephalograph (EEG), and verify them even if people don’t always recognize that they have dozed off. When people close their eyes, brain activity starts to change into an alpha pattern, the very first stage of sleep. This progresses into theta waves, which repeat in four to six cycles per second. During microsleeps, the brain is already in theta-wave mode.

How often and how quickly people slip into microsleeps depends on a variety of factors, the most important of which is the person’s sleep history. Sleep deprivation can cause more episodes, as well as a change in the body’s sleep-wake cycle — such as picking up a night shift after working during the day.

And just because microsleep occurs at the earliest stage of sleep doesn’t mean people are aware or able to pay attention to what’s around them. “In terms of performance and maintaining attention, you might as well be in the deepest sleep because the attention system [during microsleep] is not functioning with respect to the task at hand,” says Christopher Drake, chairman of the National Sleep Foundation and a member of the bioscientific staff at the Henry Ford Hospital Sleep Center.

During microsleep, however, some automatic behaviors may be possible — think about the last time you dozed off during a meeting or might have fallen asleep while driving — you might still be holding a pen or pressing the accelerator, despite the fact that your brain was no longer paying attention. But those actions don’t necessarily indicate conscious activity. “Once theta bursts occur, you really begin to lose consciousness,” says Drake.

Swedish researchers once hooked train engineers on 10-hour rides to EEG machines and noted that throughout their shift, while at the controls, the engineers had several bursts of theta-wave activity, indicating brief moments of sleep.

Whether the same thing happened to Rockefeller isn’t clear yet, but Sharkey says the tragedy should be a reminder to everyone about the dangers of sleep deprivation and drowsiness, especially for those who drive long distances. “Sleepiness should be raising a big red flag for people,” she says.

Some people aren’t aware of falling into microsleeps, and about half of those who drop off into the first stages of sleep in a sleep lab will not say they had fallen asleep. “When people are sleepy, they are impaired and bad at judging their own sleepiness,” she says. And whether it’s three-second microsleeps or deeper sleep in which all of our senses are shut down, our brains aren’t as aware or able to pay attention to what’s happening around us.