After a Green Line trolley rear-ended another train in Newton in 2008, killing the operator, the National Transportation Safety Board said the line lacked a safety system that could have prevented the accident and recommended that the MBTA install the anti-crash technology.
On Saturday, the NTSB was headed back to Boston for yet another Green Line crash, its third investigation on the subway line since 2008 and the safety system it recommended 13 years ago remains a work in progress. It will be another three years before that work is expected to wrap up.
One rail safety consultant said Saturday that the delay is another mark against the MBTA.
“Sadly, the MBTA does not have a great history of safety,” said Keith Millhouse, former chairman of the board of directors for Metrolink, a commuter rail system in Southern California.
“It’s completely inexcusable,” according to Millhouse, for any US rail system to not have safety technology to prevent train-to-train collisions. In 2015, Metrolink became the first American passenger rail system to install the technology across its network.
Friday night, 25 people, including the four MBTA operators aboard the two trains, were taken to area hospitals following the collision just after 6 p.m., which happened on Commonwealth Avenue in front of the Boston University campus.
The people were injured after one of the westbound trains struck the train in front of it, damaging the trolleys and tracks on the Green Line’s B Branch.
Massachusetts General Hospital and St. Elizabeth’s Medical Center treated the injured.
Five people sent to MGH were treated and released, a spokeswoman said. Messages left for St. Elizabeth’s weren’t returned Saturday.
Based on developments in the investigation, the MBTA on Saturday placed one of the train operators, who was not identified, on paid administrative leave, said spokesman Joe Pesaturo.
The operator, who has been working for the MBTA for seven years, was piloting the first car of the two-car trolley that struck the Green Line train from behind.
The Suffolk district attorney’s office is also looking into the circumstances of the collision, a spokesman said.
“We hope for a full and speedy recovery to all those injured or impacted by this crash,” said Matthew Brelis, a spokesman for the office.
The Boston Carmen’s Union, which represents the largest share of MBTA workers, said Saturday evening that it would closely review the results of the investigation.
The collision shared similarities with the fatal crash in Newton that claimed the life of Ter’rese Edmonds, 24, on May 28, 2008, after she went through a stop signal at 38 miles per hour and crashed into a train that was stopped in front of her. NTSB investigators also concluded that Edmonds probably suffered from fatigue and may have momentarily fallen asleep, but also faulted the MBTA for not investing in safety technology that could have prevented the tragedy. The technology, broadly referred to as positive train control, is designed to stop a train if it’s approaching a signal, obstacle, or another train too quickly.
“If technology exists — and it exists on the other lines — why would the Green Line not have everything possible that is going to prevent the accidents from happening?’’ asked Mark V. Rosenker at a 2009 NTSB meeting to discuss the Newton crash. Rosenker was acting chairman of the board at the time.
On May 8, 2009, a Green Line train rear-ended another train near Government Center, injuring 49 people and causing nearly $10million in damage.
In that case, the NTSB faulted the train operator, Aiden Quinn, saying he was texting at the time of the crash, but also noted that the Green Line still lacked the safety system. In the wake of the crash, the MBTA prohibited operators from carrying cellphones while on the job.
On Saturday, Pesaturo said installation of the $170 million safety system is expected to begin early next year.
The technology is already in place on the Red, Blue, and Orange lines, Pesaturo said. It has also been installed on the commuter rail system, as required by a federal law passed in 2008, according the MBTA website.
Getting the system into the Green Line, the oldest part of the MBTA, has proven to be more difficult.
The latest wrinkle has the MBTA’s vendor asking the Federal Communications Commission for a waiver for a radio frequency used in its safety system.
The news website Universal Hub first reported on the waiver request Friday night. The vendor, BBR Verkehrstechnik GmbH of Germany, made the request on July 2.
“The BBR system, installed on the MBTA Green Line, will provide life-saving information to ensure passenger safety,” the company wrote in its request.
Pesaturo said the MBTA expects the waiver will be granted and that the issue won’t interfere with plans to complete the work by 2024.
At the crash site Saturday afternoon, a 25-yard strip of police tape blew in the wind next to the inbound tracks, the only visible evidence remaining from Friday evening’s crash.
Matt Benoit, who witnessed the crash while working at Firestone Complete Auto Care, recalled hearing a commotion and then stepping outside the shop to see if he could help.
“I thought it was a car crash at first,” he said Saturday. “Who expects a train to crash?”
Benoit said he returned to his desk to call 911, but heard sirens before he got the chance to dial.
He said he wants to see what the investigation uncovers.
“It’s just not a good look for the city,” Benoit said.
Shuttle buses replaced trains between the Kenmore and Washington Street stops on the Green Line for much of Friday evening following the crash, the T said. Regular train service resumed at 6:20 a.m. Saturday.
Globe correspondents Jack Lyons and Charlie McKenna contributed to this report.