A MassDOT report concludes the driver of the infamous train was to blame for it heading towards town by itself, but notes the T is also aiming to fix the condition that led him to leave the train in the first place - problems with an old cabling system leased from Verizon that was making signals fail and trains stop on the tracks south of North Quincy.

The Signals & Communications Department has appropriated funds to extend a signal trough from North Quincy to Braintree Station. This would replace the existing, aging data cables and provide a more robust signal without reliance on Verizon services.

The report, publicly released yesterday, says operator David Vazquez wrapped his cab's microphone cord around the trains controller, defeating the purpose of its "dead man's switch" so he could put on some gloves as his train left Braintree station shortly after 6 a.m. on Dec. 10.

He didn't get far: The train stopped just outside the station because of a malfunction in the Red Line signaling system in that region - a malfunction that had been deviling riders for a couple of days before Vazquez's train started galloping toward the Neponset River.

Red Line cars have a switch that lets trains continue through malfunctioning signals, at a maximum speed of 25 m.p.h., but it's located on the outside front of the cars. After getting permission from the Red Line operations control center (OCC), Vazquez jumped out to flip the switch - after forgetting to unwrap the microphone cord and forgetting to set the train hand brake.

In its report, MassDOT notes the signals had been failing because of a problem in the cables leased from Verizon in that stretch of the Red Line:

Prior to the incident, from December 8 through December 10, 2015, both the Normal and Standby MBTA equipment logged communication and signal failures. The failures were intermittent, lasting from 20 seconds to a couple minutes at a time. On December 8, in response to the failures, maintainers tested and rebooted the MBTA Programmable Logic Controllers (PLCs) to troubleshoot the faults. After testing, MBTA equipment was found to be functional and the failures were attributed to a poor connection on the leased Verizon signal network.

The report continues that the T had to spend $500 to replace a door window a passenger was trying to kick out in an escape attempt as the train sat dead on the tracks - stopped by having the power on the track shut - just past North Quincy station. The first inspector who got on the train - using a southbound train commandeered from service:

Determined that passengers expressed concern as to the whereabouts of the operator, but did not seem particularly alarmed or distressed by the event. There was no indication of panic.

MassDOT also praised supervisors at the operations control commission for dealing with something they'd never dealt with before in a calm manner that prevented what could have turned into a catastrophe:

The investigation confirmed that the OCC and power dispatch teams under the direction of Mark G. McNeil, OCC Supervisor, effectively and safely brought the subject train consist to a stop, utilizing a series of actions to clear the track way of potentially conflicting trains, and power disruptions to eliminate propulsion. The processes used were based on best practical judgment, falling outside the scope of established rules, procedure, special orders or practices. MBTA Safety’s analysis of unattended train movement incidents nationally and internationally determined that such unattended incidents resulted in either a derailment or collision with another train, equipment or stations. The consequences of such events entailed loss of life, injuries and damages. The actions of the OCC and power dispatch teams are not only commendable, but represent a highly effective risk crisis management process to address a volatile and transient event. The lessons learned benefits of the team’s effectiveness in handling this circumstance should be incorporated into future training and procedural improvements.

Complete MassDOT report, via WBUR.