On May 28, 2008, about 5:51 p.m., eastern daylight time, westbound Massachusetts Bay Transportation Authority (MBTA) Green Line train 3667, traveling about 38 mph, struck the rear of westbound MBTA Green Line train 3681, which had stopped for a red signal. The accident occurred in Newton, Massachusetts, a suburb of Boston. (See figure 1.) Each train consisted of two light rail trolley cars2 and carried two crewmembers—a train operator at the front of the lead car and a trail operator in the second car. The operator of the striking train was killed; the other three crewmembers sustained minor injuries. An estimated 185 to 200 passengers were on the two trains at the time of the collision. Of these, four sustained minor injuries, and one was seriously injured. Total damage was estimated to be about $8.6 million.
We determined that the probable cause of the May 28, 2008, collision of two Massachusetts Bay Transportation Authority Green Line trains in Newton, Massachusetts, was the failure of the operator of the striking train to comply with the controlling signal indication, likely as a result of becoming disengaged from her environment consistent with experiencing an episode of micro-sleep. Contributing to the accident was the lack of a positive train control system that would have intervened to stop the train and prevent the collision.
We made new recommendations to the Federal Transit Administration, all U.S. rail transit agencies and the Massachusetts Bay Transportation Authority.
