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A subway train that derailed near Boston earlier this month had entered a 10 mph zone traveling at 36 mph, according to an initial report from the National Transportation Safety Board released Wednesday.

The Green Line train that left Lechmere Station in Cambridge and entered the zone at more than three times the posted limit passed through a double red signal that requires a stop and reached a switch that was still moving to direct the train to a diverging track, according to the report.

When the train passed over the switch, the first wheel sets of the leading railcar continued straight, while the next two wheel sets of the same railcar took the diverging track and derailed.

The derailment occurred Oct. 1 during the afternoon commute. Seven passengers were taken to a local hospital with minor injuries. Damage estimates were still being determined.

Visibility conditions at the time of the accident were clear, according to investigators. The weather was about 62 F with no precipitation.

The NTSB’s probe is ongoing. Further investigation will focus on compliance with speed rules and internal and external oversight, according to the agency.

Officials at the Massachusetts Bay Transportation Authority said the transit agency is reviewing the preliminary report.

“The NTSB has affirmed the MBTA’s initial assessment that the Green Line train operator was exceeding the posted speed limit at the time of the derailment,” the agency said in a written statement.

“The train operator remains out of service while the MBTA Safety Department completes its own investigation. The safety and well-being of MBTA riders and employees are of the utmost importance,” the agency said.

MBTA trains are monitored on all surface lines using GPS technology, and real-time information is sent to all Green Line supervisors if a train is traveling more than a set speed threshold, officials said.

There are nine stationary speed signs placed at different locations on the Green Line. The signs help identify the speed of a vehicle and compare it to the programmed posted speed limit.

However, Green Line trains lack so-called “train protection systems” that are standard on most of the world’s subway systems. These systems, typically mounted on individual trains, automatically stop or slow a train if they sense it’s going too fast or if it’s getting too close to another train, effectively eliminating the possibility of driver error.

Successive NTSB investigations of crashes on the Green Line have recommended the agency add train protection systems since a fatal incident in 2009, but it took until January 2019 for the agency, under a previous general manager, to green-light an $83 million contract to buy a system for the Green Line.

Current MBTA General Manager Phil Eng terminated that contract in July of this year after the vendor, German rail technology firm BRR, failed to deliver after being acquired by a competitor. The agency issued a new request for proposals at the same time, with responses due at the end of August.

“Additionally, this derailment highlights the urgent need for the long-overdue overhaul of the Green Line’s signal system. An upgraded system would likely have mitigated the overspeed that led to this derailment and could prevent similar incidents from occurring in the future. Signal modernization must remain a top priority for the T, which requires sustained financial and operational commitment,” watchdog group TransitMatters said in a statement that urged the T to undertake a “thorough review” of its training, oversight and switch design.

“Lastly, we caution the MBTA against implementing performative or reactionary “safety measures” that would unnecessarily disrupt service on the Green Line without addressing core issues. Genuine improvements come from long-term, sustainable solutions, not quick fixes,” the group added.

MBTA officials said the agency has stepped up its focus on compliance with operating rules, including adherence to posted speed limits.

Operators found to be in violation of the rules are disciplined, according to MBTA officials.

Image courtesy of the NTSB

Banker & Tradesman staff writer James Sanna contributed to this story.