On May 28, 2008, about 5:51 p.m., Eastern Daylight Time, westbound Massachusetts Bay Transportation Authority Green Line train 3667, traveling about 38 mph, struck the rear of westbound Green Line train 3681, which had stopped for a red signal. The accident occurred in Newton, Massachusetts, a suburb of Boston. Each train consisted of two light rail trolley cars 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. In the course of its investigation of this accident, the NTSB identified the following safety issues: lack of a positive train control system on the Massachusetts Bay Transportation Authority light rail system, lack of coordination between crewmembers on Massachusetts Bay Transportation Authority light rail trains with regard to signal indications, inadequate requirements for Massachusetts Bay Transportation Authority train operators to report possible signal malfunctions, and lack of screening of rail transit operators for possible obstructive sleep apnea. As a result of its investigation of this accident, the NTSB makes recommendations to the Federal Transit Administration, all U.S. rail transit agencies, and the Massachusetts Bay Transportation Authority. The National Transportation Safety Board also reiterates one safety recommendation to the Massachusetts Bay Transportation Authority.