A short circuit on a Red Line train prevented a failsafe from triggering and allowed the vehicle to leave the station while a passenger was trapped in a door, federal investigators concluded while describing a pair of other missteps in the fatal incident.

The National Transportation Safety Board (NTSB) last Tuesday (June 27) deemed the short circuit the “probable cause” of the April 10, 2022 tragedy that killed a man named Robinson Lalin.

Red Line trains like the one involved in the accident are equipped with interlock circuits that disable propulsion if any passenger door is open, including if the door is blocked. But an NTSB investigation of the vehicle in question found that protruding wire strands touching a mounting screw created a short circuit, effectively allowing the train to move before its doors fully closed.

“Under normal operating conditions, the passenger door interlock circuit would have prevented train propulsion if a door obstruction was detected or the doors were open,” the agency wrote in a 10-page report. “However, the short circuit that bypassed the passenger door interlock circuit allowed the train to proceed even with the passenger’s upper body obstructing the ... railcar doors.”

The agency tested its entire Red Line fleet within 72 hours of Lalin’s death and found no similar issues, according to the NTSB. An MBTA spokesperson said similar tests performed on all Orange, Blue, and Green Line vehicles did not identify another problem.

Investigators determined the short circuit occurred at some point after the master controller was rebuilt in 2017. The NTSB said that at the time of the accident, the MBTA’s preventative maintenance did not include an inspection procedure to examine the door interlock circuit’s functionality.

After the incident, the T updated its maintenance process to include testing to ensure trains could not begin travel while doors were open. The agency also implemented a new electrical isolation method on the relevant terminal boards to ensure that “protruding wires do not unintentionally complete a short circuit,” the NTSB wrote.

The report, which builds on the NTSB’s preliminary findings issued in May 2022, noted that Lalin and several other passengers boarded a Red Line train at Broadway Station just before 12:30 a.m. on April 10, 2022. Lalin attempted to disembark while the train was departing when the doors closed on his “upper body on his right side.” He ran alongside the train while trapped in the door, then collided with a wall at the end of the platform and was killed, the NTSB said.

MBTA departure policy requires operators to stick their heads outside of the operating cab and make sure the platform is clear before departing and to check that pilot lights are off, which indicates that passenger doors have closed, according to the report.
The NTSB found that the operator of the train conducted a visual inspection of the platform but pulled her head back into the cab before the pilot lights above the malfunctioning door turned off, “contrary to MBTA departure procedures.”

An MBTA spokesperson said the operator no longer works for the T but did not say if the operator had resigned or was terminated.

The NTSB also found a 19-foot “blind spot” in a camera view of the station platform, which blocked sight of the door in which Lalin became trapped. If the operator was using a monitor with that camera feed to check the platform, “it was unlikely that she would have seen Lalin stuck in the doors,” investigators said.

In the wake of the accident, MBTA officials began conducting regular audits of those cameras and monitors, referred to as single-person train operation (SPTO) cameras. T spokesperson Lisa Battiston said the agency has upgraded and replaced 31 of 55 monitors with “larger, brighter, and easier to clean” versions, focusing first on those in “the most critical locations.”

“This includes upgrading and replacing both SPTO monitors at Broadway station,” Battiston said. “The MBTA has also been implementing a Legacy Camera Replacement project, funded by a Department of Homeland Security grant, to phase out aging equipment. Additionally, the MBTA has also improved communications between motor persons and the team responsible for maintaining the cameras and monitors to ensure that any issues are resolved quickly.”