NTSB executive summary of findings in Green Line crash

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.

The safety issues identified during this accident investigation are as follows:

• 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 National Transportation Safety Board 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.

CONCLUSIONS

1. The following were neither causal nor contributory to the accident: weather conditions, equipment performance, track condition, crewmember use of alcohol or illegal drugs, crewmember use of cell phones, crew training and qualifications, or the performance of the crew of the struck train.
2. The emergency response to this accident was timely and appropriate.
3. The operator of the striking train was at a high risk for having undiagnosed sleep apnea, and she may have been chronically fatigued as a result of the condition.
4. The operator of the striking train failed to respond appropriately to the controlling signal indication or to take advantage of several opportunities to slow or stop the train and to prevent the accident likely because she experienced a micro-sleep episode after departing Waban station.
5. The Massachusetts Bay Transportation Authority continues to have an inadequate fatigue awareness program to educate train operators about the risks of fatigue and an inadequate program to identify and address potential sleep disorders for its train operators.
6. The broken bonds associated with signal H-66 caused a delay that placed train 3681 in a position to be struck by train 3667.
7. Because Massachusetts Bay Transportation Authority operating rules do not require that train operators report signals displaying red when the block of track governed by that signal can be determined to be unoccupied, possible problems in the signal system could remain undetected and unrepaired, which could increase safety risks on the rail line.
8. Had the Massachusetts Bay Transportation Authority required train operators to inform trail operators of restrictive signal indications and had the operator of the striking train informed her trail operator of the restrictive signal indication just west of Waban station, the trail operator might have been able to prevent the accident by questioning the operator about the train speed or by applying the brakes.
9. This accident could have been prevented had the Massachusetts Bay Transportation Authority Green Line been equipped with a positive train control system that could have intervened to stop train 3667 before it could strike the rear of train 3681.
10. The failure of the structure of the trolley cars resulted in the catastrophic loss of survivable space.
PROBABLE CAUSE

The National Transportation Safety Board determines 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.

RECOMMENDATIONS

As a result of its investigation of the May 28, 2008, collision between two Massachusetts Bay Transportation Authority Green Line trains, the National Transportation Safety Board makes the following safety recommendations:

NEW RECOMMENDATIONS

To the Federal Transit Administration:
1. Facilitate the development and implementation of positive train control systems for rail transit systems nationwide. (R-09-XX)
2. Develop and disseminate guidance for operators, transit authorities, and physicians regarding the identification and treatment of individuals at high risk for obstructive sleep apnea and other sleep disorders. (R-09-XX)
To all U.S. rail transit agencies:
3. Review your medical history and physical examination forms and modify them as necessary to ensure that they elicit specific information about any previous diagnosis of obstructive sleep apnea or other sleep disorders and about the presence of specific risk factors for such disorders. (R-09-XX)
4. Establish a program to identify operators who are at high risk for obstructive sleep apnea or other sleep disorders and require that such operators be appropriately evaluated and treated. (R-09-XX)
To the Massachusetts Bay Transportation Authority:
5. Require that train operators immediately report to the train dispatcher any inappropriately displayed aspects and all red signal aspects they encounter when the block of track governed by that signal can be seen to be clear of other trains. (R-09-XX)
6. Require train operators to notify other train crewmembers when the train encounters a restrictive signal and to inform crewmembers of the operator’s intended means of complying with the restrictions. Include a requirement that the other crewmembers acknowledge receiving this notification. (R-09-XX)
7. Develop and implement a positive train control system for all of your rail lines. (R-09-XX)
RECOMMENDATION REITERATED IN THIS REPORT
To the Massachusetts Bay Transportation Authority:
R-01-27

Ensure that your fatigue educational awareness program includes the risks posed by sleeping disorders, the indicators and symptoms of such disorders, and the available means of detecting and treating them.

RECOMMENDATION RECLASSIFIED IN THIS REPORT
To the Massachusetts Bay Transportation Authority:
R-01-27

Ensure that your fatigue educational awareness program includes the risks posed by sleeping disorders, the indicators and symptoms of such disorders, and the available means of detecting and treating them.

Safety Recommendation R-01-27, previously classified “Open—Acceptable Response,” is reclassified “Open—Unacceptable Response” in the “Performance of the Operator of the Striking Train” section of this report.