System designed to keep Green Line trolleys from plowing into each other is finally under contract, but still years away

Green Line crashes in 2008 and 2009 - one fatal - slowly spurred the MBTA to hire contractors to equip the nation's oldest subway line with a system that would automatically brake trolleys whose operators run red lights or seem about to smash into another trolley and who disregard audible alarms to stop.

But the German company hired in May, 2020 to build out the Green Line Train Protection System only applied this year for the required waiver to use a particular radio frequency from the Federal Communications Commission, needed for the $170-million project. The project is based on recommendations from the National Transportation Safety Board in 2009.

Until the FCC waiver comes, work can't start to install the equipment both along Green Line tracks and on the trolleys to make the system operational.

Under a schedule approved last year, installation of track-side equipment was to begin this year, with testing in 2022, some actual use in 2023 and all trains running under the new system in 2025.

Along the tracks, a contractor would install sensors that would trigger an on-train system that would sound an audible alarm if a driver were to go past a red signal or failed to slow down because of a speed reduction along a particular stretch. If the trolley kept going, the system would then stop the train.

In its request to the FCC to approve the system proposed by BBR Verkehrstechnik, the T acknowledged that coming up with a solution for the NTSB's 2009 recommendation that the T do something to stop trolleys from colliding - which came after a similar 2008 recommendation - "has taken quite a while" but urged the FCC to act quickly "based on the criticality of addressing this safety recommendation."

What got the T to thinking about a system analogous to the ones long in use on the Red, Blue and Orange lines and installed in recent years along commuter lines, were two particular crashes: One on the D Line in Waban in 2008 that killed the driver who hit another trolley stopped for a red signal after she went into what federal investigators called "micro-sleep" and a crash in the tunnel near Government Center in 2009 caused by a trolley driver too busy texting his girlfriend to notice the red signal he blew by.

The crashes caused dozens of passenger injuries and millions of dollars in trolley damage.

In its reports on both incidents, the NTSB urged the T to install a "positive train control system" that might have prevented further crashes, such as a 2012 crash at Boylston that injured several dozen riders and was caused by a driver who hadn't gotten any sleep after getting off a second job overnight before the crash - and, possibly, today's B Line crash.