A Green Line trolley was traveling more than three times the speed limit and passed through a stop signal in the moments before a derailment that injured seven passengers, federal investigators said.
The National Transportation Safety Board on Wednesday published preliminary results of its investigation into the Oct. 1 MBTA derailment, finding that the train that came off the tracks just outside Lechmere Station was moving far faster than the allowable speed over a switch that was still moving.
“Less than a minute before the derailment, the train departed Lechmere Station in Cambridge, Massachusetts, and headed east along the MBTA Green Line. The train entered a 10-mph zone at 36 mph, passed through a double red signal (which requires a stop) west of the Red Bridge interlocking, and reached a switch that was still moving to direct the train into the diverging track as required by its route,” the NTSB wrote. “When the train passed over the switch, the lead truck of its leading railcar continued straight, while the next two trucks of that same railcar took the diverging track and then derailed.”
About 50 passengers and two MBTA employees were on board the train. Seven passengers were transported to the hospital with minor injuries, according to the NTSB, and investigators are still working to determine how much damage the incident inflicted.
Officials noted the weather was about 62 degrees with no precipitation and clear visibility at the time of the accident.
An MBTA spokesperson said Thursday that the operator involved in the incident “remains out of service while the MBTA Safety Department completes its own investigation.”
The Green Line features nine stationary speed signs at different locations, and surface trains are also monitored in real time by supervisors using GPS and Lidar, an official said. Employees found to be above the speed limit but below a 6 mile per hour overspeed threshold three times in a 12-month period are sent to reinstruction.
The NTSB interviewed witnesses, reviewed data from event recorders above the train and on signals and cameras, and inspected railroad equipment and tracks.
“Future investigative activity will focus on speed rules compliance and internal and external oversight,” the federal agency said.
