NEW INFORMATION was released on Tuesday dealing with two recent incidents on the MBTA – one involving a July 30 collision on the Green Line in Brookline and the other a March 16 derailment of a new Orange Line vehicle near Wellington Station in Medford.

The National Transportation Safety Board issued a preliminary report on the Green Line collision concluding that the driver of one train put the master controller in a full-power position and was traveling at a speed of 31 miles per hour when it slammed into another vehicle just ahead traveling in the same direction at 10 miles per hour. The speed limit in the area was 10 miles per hour.

As a result of the accident, 24 passengers and three crew members were transported to the hospital with minor injuries.

The latest information continues to point to the operator of the trailing vehicle as the cause of the accident. The employee, who has not been identified, was placed on administrative leave the day after the collision and suspended without pay on September 20. The T is now moving to fire him.

“The MBTA and Transit Police will continue to work with the Suffolk County District Attorney’s office in its ongoing investigation into the trolley operator’s actions,” according to a statement issued by T spokesman Joe Pesaturo. “The MBTA thanks the NTSB investigators for their diligence and hard work in establishing the facts surrounding the collision. The MBTA is taking the steps necessary to end the employment of the individual involved in the collision.”

The T is also installing a $170 million anti-collision system on the Green Line that will alarm if one vehicle is nearing another and trigger automatic braking if the vehicles get too close. The system is expected to be operational in 2024.

After the derailment of the new Orange Line train near the Wellington T station, the T took all new Orange and Red Line trains out of service. Pesaturo said some of the new vehicles are now returning to service even though a final report on the cause of the derailment has not been completed.

According to Pesaturo, three new Orange Line trains have been returned to service, and a fourth will be back next week.  The new Red Line cars that have been on the sidelines should return to service in December, he said.

In early June, the last time T officials addressed the derailment, Deputy General Manager Jeff Gonneville said no one issue appeared to be the cause and he acknowledged that the T and the Chinese manufacturer, CRRC Mass., were at odds on what was the chief culprit.

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.

According to Gonneville, the T felt the derailment was caused primarily by problems with the vehicles themselves, specifically pads attached to the train trucks that enable the vehicles to turn. Gonneville said the pads were wearing down faster than expected, which causes the pads to grip harder, increasing rotational force that makes it more difficult for vehicles to turn.

Gonneville said other issues were also at play, including a 46-year-old switch that lacked a guardrail designed to keep vehicles on the track and other issues with the track itself.

“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,” Gonneville said in June. “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.”