On portions of tracks adding up to more than a mile, Green Line Extension trains are moving at only three miles-per-hour. The MBTA says these slow zones are a response to recent tests showing that portions of the tracks are narrowing. A concept that many transit experts say is unheard of.

Boston Globe Transportation Reporter Taylor Dolven broke this story last week. She joins' The Common with more on what we know, and don't know, about the condition of the GLX, and how it's impacting the communities that rely on it. 

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