by Disney Guy
From observing the signals' behavior I would guess that on the Green Line, the timers for some red signals equipped with them do not start counting down until the train is almost at that signal. Or maybe there is just a plain sensor with no timer right at the signal.
Compared with on the Blue Line where a timer is usually activated long before the train reaches the signal and the operator can adjust his speed to not have to stop at a red signal.
Some timed signals will clear from red to green if the track is clear far enough ahead.
The signal outside Waban might well have a defect. It might not be getting the condition of the next block, without which information it may not show green. That is not a high priority repair. Not getting the condition of its own block and therefore not being able to upgrade from red is a high priority item.
There exist two aspect (green and red) block signal systems. Nowadays they need additional safety measures such as a repeater head underneath for the next signal downstream, namely green over red stands for "proceed prepared to stop at next signal." The Lechmere viaduct (and I think long ago the Harvard bus tunnel) has had a two aspect signal system using yellow and red.
Compared with on the Blue Line where a timer is usually activated long before the train reaches the signal and the operator can adjust his speed to not have to stop at a red signal.
Some timed signals will clear from red to green if the track is clear far enough ahead.
The signal outside Waban might well have a defect. It might not be getting the condition of the next block, without which information it may not show green. That is not a high priority repair. Not getting the condition of its own block and therefore not being able to upgrade from red is a high priority item.
There exist two aspect (green and red) block signal systems. Nowadays they need additional safety measures such as a repeater head underneath for the next signal downstream, namely green over red stands for "proceed prepared to stop at next signal." The Lechmere viaduct (and I think long ago the Harvard bus tunnel) has had a two aspect signal system using yellow and red.
Build something. Anything.