Local inventor Nick Musachio has patented a concept called “Always Green Traffic Control”. I have mentioned it before. The short version is that traffic signals are fixed timed. The cars (and in the case of the Green Line: trains) are made aware of the speed needed to travel at to catch the green (through a variable message sign). Some cars (and the trains) comply with recommendations, as do all the cars following them, and a large platoon of vehicles can make the green. This increases the efficiency of the signal all around.
He argues this can be used for trains. Some interesting simulations of this have been posted to YouTube this week:
More simulations can be seen on his YouTube page.