IT’S BEGINNING to look like the MBTA may never pinpoint the cause of a March 16 derailment of one of its new Orange Line trains.
At a meeting of the Fiscal and Management Control Board on Monday, Deputy General Manager Jeffrey Gonneville indicated the T and the Chinese manufacturer of the trains disagree on the principal cause and that a “series of contributing factors” may ultimately be blamed for the derailment.
The stakes are high in this derailment investigation because all of the T’s 252 Red and 152 Orange line vehicles are being replaced by CRRC Mass., the Chinese manufacturer. The relatively few new vehicles delivered to the T so far have been on hold ever since the derailment and it’s still unclear when they will return.
The new Orange Line train was moving from one track to another at slow speed in a work zone near the Wellington train yard in Medford when it derailed. Initial concerns focused on aging infrastructure – a commonplace issue at the T – since the train made the move between tracks using a 46-year-old switch.
The switch was replaced along with track in the area, but Gonneville on March 29 said it was unclear if the switch was the cause of the derailment. He declined to say whether 46 years exceeded the switch’s useful life, noting it would depend on how heavily it was used over the years. “Newer is better,” he conceded at the time.
On May 10, Gonneville said he suspected the problem had to do with the vehicles themselves – specifically pads attached to the trucks which enable the vehicles to turn. He said testing indicated the pads were wearing down faster than expected. When that happens, he said, the pads tend to grip harder, increasing “rotational force” that makes it more difficult for the vehicle to turn.
On Monday, Gonneville outlined a handful of other infrastructure issues that could have played a role. He said the switch, in addition to being old, lacked a guardrail that helps to keep a train on the track in tight turns. He also outlined two other issues with the track itself that could have been contributing factors.
There was no “single point of failure” that caused the derailment, Gonneville said.
“The MBTA right now does feel pretty strongly that the guardrail itself on the switch and the excessive rotational force were more than likely the key contributing forces that led to this incident,” he said. “But in full fairness, CRRC is of the opinion that really the infrastructure items that I’ve outlined here played a greater or more key role in influencing the derailment itself.”
Gonneville said the T and CRRC both agree that the rotational forces caused by pad wear exceeded design limits. He also said the T is shutting down a stretch of the Orange Line from June 26 through July 1 to replace several more switches – including one that is heavily used near the Wellington yard — that are in similar shape to the one where the derailment occurred. He said the new switches will all have guardrails.