(Adds NTSB interview with driver)
By Jonathan Allen
NEW YORK, April 7 (Reuters) - The driver of a train that derailed in December in New York City, killing four passengers, had an undiagnosed sleep disorder at the time of the accident, the National Transportation Safety Board said on Monday.
William Rockefeller, the engineer at the controls of the Metro-North commuter train that derailed in the Bronx on Dec. 1, suffered from severe sleep apnea, which can cause drowsiness, according to documents published by the safety board on Monday.
The documents also included a transcript of Rockefeller's interview with investigators two days after the crash, which provides the fullest account yet of the "hypnotic" state he said overcame him before he realized his train was derailing.
"I was dazed, you know, looking straight ahead, almost like mesmerized," Rockefeller told investigators. "I don't know if anybody's ever experienced like driving a long period of time in a car and staring at the tail lights in front of them, and you get almost like that hypnotic feeling staring straight ahead."
The sleep apnea diagnosis came from a doctor specializing in sleep disorders and who examined Rockefeller in December at the safety board's request.
"Being a shift worker might have contributed to the accident," the doctor, who was not identified, wrote in a statement to the board, according to a medical report among the newly released documents.
The disorder, characterized by shallow or interrupted breathing during sleep, often goes undiagnosed, according to the U.S. National Institutes of Health.
Jeffrey Chartier, Rockefeller's lawyer, also confirmed the diagnosis, saying Rockefeller cooperated with investigators and provided access to his medical records.
Rockefeller's condition appeared to have been aggravated by his assignment to an early-morning shift about two weeks before the crash, Chartier said, a switch that was also noted in the report.
The medical report also said Rockefeller had small amounts of a sedating antihistamine in his bloodstream at the time of the accident.
His last routine physical examination for Metro-North was in May 2011, and his last visit to his own doctor was in May 2013, the report said.
Before the accident, doctors had diagnosed Rockefeller as obese and having hypothyroidism, high cholesterol, low testosterone, vitamin D and B12 deficiencies, and mild high-frequency hearing loss, the report said.
He had never been screened or examined for sleep apnea until after the accident, the report said.
'SOMETHING WASN'T RIGHT'
Investigators said the seven-car train was traveling nearly three times faster than the speed limit as it approached a curve in the track just outside the Spuyten Duyvil station in the Bronx. In addition to the four deaths, more than 70 people were injured.
In the newly released transcript of his interview with investigators after the crash, Rockefeller described what began as an uneventful Sunday morning, beginning with him waking up at 3:30 a.m.
At Poughkeepsie station, about 70 miles (113 km) north of New York City, he took his usual coffee and buttered roll into a routine safety briefing before he and his conductor headed to the train to do safety checks before setting off down a track he had driven up and down for seven years.
The train was operating normally and the familiar routine continued until after he left the Tarrytown station and the trance-like state took hold, Rockefeller told investigators.
He had no memory of approaching the curve with its speed limit of 30 miles per hour (50 kph), he said.
"The only thing that shook me out of it was the feeling of the train," he said, according to the transcript. "Something wasn't right with it, something, and that's when I believe instinctly (sic) I had thrown it into emergency."
The safety board on Monday also released transcripts of interviews with other Metro-North employees, along with a report by engineers who examined the accident scene. The investigation continues and the board has not released its final analysis. (Additional reporting by Curtis Skinner; Editing by Scott Malone, Bernadette Baum; Lisa Von Ahn and Dan Grebler)