Operator error and the lack of automated safety systems caused a May 2008 crash on the MBTA Green Line in Newton, according to official findings from the National Transportation Safety Board.
The operator, Ter'rese Edmonds, 24, died in the accident. Seven passengers were injured. The crash caused more than $8 million in damage.
NTSB investigators concluded that Edmonds ran through a red light near Newton's Waban Station. MBTA regulations require that operators stop for one full minute at all red signals, then proceed at 10 miles per hour. Edmonds's train was traveling at almost 40 miles per hour when it struck another Green Line trolley waiting at the next red light.
Investigators believe both lights were improperly stuck on red due to rusted wiring they found between the signals. The rust would have interrupted communication between the signals, making them go on and off incorrectly.
The trolley struck from behind had stopped at the second red signal that had been malfunctioning intermittently, investigators said.
However, even with malfunctioning lights and operator error, investigators called this an entirely preventable accident. Most of the MBTA's rail lines are equipped with some form of collision prevention technology. The Green Line does not have such control systems in place.
"Why would the Green Line not have everything possible that is going to prevent the accidents from happening?" said acting NTSB chairman Mark Rosenker. "I don't understand that as an operator. I just don't."
MBTA General Manager Daniel Grabauskas did not respond to requests for comment.
Grabauskas has previously said that collision prevention technologies — also called positive train control — wouldn't work on the Green Line due to the large number of trolleys that run at peak hours.
"Up to one-third of Green Line trains would have to be taken out of service during rush hour in order for the system to operate without any problems under positive train control," said MBTA spokesman Joe Pesaturo.
NTSB board members said the absence of collision control systems are evidence of a larger problem. MBTA operators hadn't reported the faulty signals to dispatchers as required by regulation.
NTSB board member Robert Sumwalt also questioned the T's frequency and adequacy of operator evaluations in the field. "I think it speaks to the lack of a safety culture of this organization that they did not do those kinds of things to see what was going on there out on their rail lines," Sumwalt said.
MBTA spokesman Joe Pesaturo denied the rebuke and pointed to the increased number of field supervisors deployed by the T in the past year. "Supervisors do fitness for duty tests from time to time, so a lot of that is taking place right now," he said.
Why Edmonds ignored the red signal remains an open question. Investigators found no evidence of drugs or alcohol in her system. She had a clear view of the train in front of her and more than 700 feet in which to stop. At even half that distance, at 350 feet, investigators say Edmonds would have had a full seven seconds to stop the train. Yet, there was little evidence she applied the breaks.
However, tests revealed traces of doxylamine, a compound found in common sleep aids, in her urine. Edmonds also had a body mass index of 38.5, an amount that doctors designate as clinically obese.
Investigator Rick Narvell said the two factors together suggest that Edmonds could have suffered from episodes of "micro sleep" caused by a sleeping disorder.
"The draft report concludes that the operator of the striking train was at a high risk for having undiagnosed sleep apnea," Narvell said. "And she may have been chronically fatigued as a result of that condition."
NTSB board members stressed that they cannot conclude with certainty that Edmonds had a sleeping disorder. However, sleep apnea played a significant role in four recent crashes across the country.
The board's final report recommends the MBTA significantly enhance fatigue awareness education and sleep disorder screening of all train operators.
This program aired on July 15, 2009.