WASHINGTON — An operator’s failure to obey a stop signal was the probable cause of an Oct. 1, 2024, derailment of a Massachusetts Bay Transportation Authority light rail train in Somerville, Mass., the National Transportation Safety Board said in its final investigation report released this month. The train’s excessive speed was a contributing factor, according to the report.
Approximately 50 passengers and two operators were on board the Green Line train when the accident occurred about 4:46 p.m.; seven passengers were transported to the hospital with minor injuries [see “Seven taken to hospital …,” Trains.com, Oct. 1, 2024]. The two-car light rail trainset was traveling about 36 mph when it entered a 10-mph zone from a 30-mph zone. It then passed a double-red signal requiring a stop near the Red Bridge interlocking, and derailed when it split a switch that was still in the process of moving to direct the train onto its planned route.
The incident caused an estimated $1.5 million in damage.
The train’s operator, when interviewed by NTSB investigators, said he did not know how fast the train was moving and said, “to the best of my knowledge I had the proper routing signal.” The investigation also found that the operator’s mobile phone indicated incoming and outgoing calls and text messages while the operator was on duty; one text message was received just a few seconds before the derailment. The investigation also found that one speed-limit warning sign was posted nearer the reduced-speed zone than is required by the MBTA, but noted this was not a factor because there is “no evidence … that the operator attempted to respond to the signage at all.”
While the report says the operator’s actions are consistent with distraction, it says there is not enough evidence to identify a potential cause. The light rail equipment did not include an inward-facing camera or audio camera that the NTSB says could have provided additional evidence. It also says an Automatic Train Control system could have prevented the accident.
This is the first of two similar MBTA accidents under investigation by the NTSB. The agency also has an ongoing investigation into a Feb. 9, 2025, collision between two Green Line trains in Somerville. The preliminary report on that incident indicates that one of the trains involved also was speeding and passed a red signal before hitting a stationary vehicle [see “MBTA Green Line train was speeding …,” Trains.com, March 6, 2025].
