They will have to fix Boston’s horribly broken subway system first.
Here's a graph of slow zones:
https://old.reddit.com/r/boston/comments/11qtx82/red_line_sl...
They are returning a good chunk of the system back to regular service this Summer, though.
Edit: the slow zones might not be clear on that graph, but at one point the Red Line end-to-end was around 1-1.5 hours slower. Especially bad for commuters.