The National Transportation Safety Board says a sleep-deprived engineer nodded off while at the controls, causing the fatal Metro-North train derailment last year in Spuyten Duyvil.

The NTSB released its report on the December 2013 accident Tuesday, blaming engineer William Rockefeller and a lack of technology. The NTSB says Rockefeller fell asleep due to a combination of sleep apnea and a change in his work schedule. The train, going 82 mph, came off the tracks and hit a curve with a 30 mph speed limit. Four people were killed and more than 70 were injured.

The report also found the train did not have positive train control, technology that can automatically stop a train exceeding the speed limit. Metro-North says it is now working to install the technology on its trains.

The NTSB also issued rulings on four other Metro-North accidents that happened in the past year, and the railroad was repeatedly found at fault. In a statement, Metro-North President Joseph Giulietti says "Every decision and change that has been made since I became president last February has been made to advance safety. Our goal is to build a culture of safety where each employee is responsible for the safety of every customer and every other employee."



The NTSB says it will meet in Washington, D.C. next month to make formal recommendations for Metro-North to improve its safety.