Page:Derailment of Amtrak Passenger Train 188 Philadelphia, Pennsylvania May 12, 2015.djvu/59

NTSB ==Board Member Statements== Chairman Christopher A. Hart filed the following concurring statement on May 20, 2016.

I concur with the findings, probable cause, and recommendations in this report, and I would like to comment on what this accident demonstrated not only about the importance of Positive Train Control (PTC), but also the importance of how PTC is implemented.

PTC. This accident demonstrated once again that PTC can save lives. Our investigators explored all of the usual suspects regarding the engineer's condition – fatigue, impairment from alcohol or other drugs, and cellphone use – and found none of them. However, we have investigated many accidents in which an operator's thought processes were interrupted, and even when a checklist was being used, the thought processes missed a step or two because of the interruption. This accident is reminiscent of a bus accident we investigated in which the bus driver was distracted by looking into her rear view mirror to determine if it was safe to change lanes – which is certainly important in order to change lanes safely – only to crash into vehicles that had stopped in front of her. In Amtrak 188, it was not only appropriate but required for the engineer to pay attention to the disabled train, to determine, among other things, if he needed to slow down and/or sound his horn while passing that train. By process of elimination, we concluded that the distraction of the engineer diverting his attention to the disabled train interrupted his thought processes and caused him to lose situational awareness. The engineer was distracted, but the distraction was about something that he had a duty to take care of – passing the disabled train safely. This demonstrates once again that even when a person is competent (as he was, with extensive experience on the route and an unblemished record), not fatigued, not impaired, and not using his cell phone, he or she is still fallible, even on his or her best day. PTC is crucial, and we have recommended it, or something like it, for more than 45 years, because it is a backup, a safety net, for inevitable human fallibility.

Implementation of PTC. Having said that, we have also investigated accidents that demonstrated that introducing automation into a complex human-centric situation can present many challenges. Those challenges can be exacerbated when, as here, the automation is partial instead of complete. In this instance, the curve where the derailment occurred had automatic speed protection in one direction, but there was no speed protection for trains going in the direction of Amtrak 188.

Amtrak explained this speed protection disparity by noting that the permitted speed limit approaching the curve in the other direction exceeded the derailment speed, whereas the permitted speed limit approaching the curve in this direction was less than the derailment speed. Experience has shown, however, that partial automation can be more dangerous than no automation at all. 49