But investigators said they were unable to determine why Brody drove her car onto the tracks despite warning signs indicating a train was approaching.
Robert Sumwalt, an NTSB board member, said he thinks Brody simply "lost situational awareness."
"Sometimes we cannot explain human behavior, especially when we don't have the person to talk to," Sumwalt said. "I don't believe she knew she was at the railroad track. She didn't realize where she was. Had she known she was in harm's way, she would've fled the vehicle or she would've run."
The NTSB met Tuesday morning in Washington, D.C., to discuss its investigation and determine the probable cause of the February 2015 train crash.
Brody, 49, of Edgemont, N.Y., had left her job in Chappaqua before encountering a traffic jam along the Taconic State Parkway in Mount Pleasant that followed a head-on collision. With bumper-to-bumper traffic detoured over railroad tracks at Commerce Street, Brody briefly stepped out of her Mercedes SUV to check a crossing gate that had come down on the rear of her car.
She then moved forward onto the tracks, where she collided with the train. Had she not moved her car forward, the collision would have been minor, the NTSB said. The train horn could be heard from 350 feet away and the warning system operated as designed, the NTSB said.
The NTSB said it spent a considerable amount of time trying to understand Brody's mindset.
"There are numerous possibilities," Kenny Bragg said. "A lot of these things we are not able to determine because the only person who can speak to this is Ellen Brody. We examined every circumstance, and there is not a definitive conclusion."
Board members debated whether to use Brody's loss of "situational awareness" be included as a probable cause.
The third rail penetrating the passenger compartment of the first train car and a post-accident fire also led to fatalities and injuries, the NTSB said. The railroad signaling system played no role in the accident, the NTSB said.
Brody was not under the influence and she had no medical conditions that contributed to the crash, the NTSB said.
The crash was the deadliest incident in Metro-North's history.
U.S. Sen. Richard Blumenthal (D-Conn.) said Metro-North must address "the urgent need to address catastrophic risks posed when third rail is present at grade crossings."
"Metro-North must take immediate action to eliminate that glaring hazard to ensure the chaos and carnage we saw in 2015 can never be repeated,” Blumenthal said.
“This grade crossing was a deadly disaster waiting to happen. While aspects of this tragedy may be unique, the tragic truth is that hundreds of lives are lost each year in grade crossing collisions due to poor design and inadequate education," he said. "That is why I will reintroduce legislation this year to finally bring grade crossings into the 21st century through better education, enforcement and engineering."
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