I smell bullshit.
Much heavier trains than the Green Line run in all sorts of conditions where they cannot see the signal after the current one, and without any form of PTC or CBTC. And have done so for over a century. That's why signals exist in the first place.
Yes. There have been lines operating with automatic stops for over 100 years. That's NYC Subway and every heavy rail clone in the world. And many of them--such as NYC Subway and the Blue Line--still do old-timey mechanical stops where a trip arm springs up from trackside and physically strikes a target under the train to send it into an auto-stop if the operator doesn't obey the traffic-light style wayside signals.
Green doesn't have that. There are no enforced stops; the human operator can obey or disobey the wayside signals just like they can obey or disobey a traffic light on Huntington Ave. Some other LRT systems have grade separated portions or subway portions that operate the same way. The only difference between them and the Green Line is that the Green Line is the
busiest and
densest-headway such example of an unenforced rapid transit line currently operating in the world.
This isn't news. You're not raising a complaint, you're just describing the basic dictionary-definition difference between ATC and non-ATC operation as it's been practiced around the world for the last 100 years..
The signal exists to tell the train operator that the block is clear. The block is clear, the operator can enter it. Now if the stopping distance is too long, then you have a signal design that indicates whether the following two blocks are clear. Yeah, the Green Line doesn't have that. So what they could do is move at restricted speed until the next green signal. Not a full, obviously pointless stop.
No, because the Green Line--being the busiest non-ATC system in the world--doesn't have a mechanism to force 100% compliance at the highest-risk spots. Before Arlington outbound you've got the downgrade and slight curve on the downgrade creating a speed-trap situation on an obstructed-view stretch where braking distance is going to be compromised by speeding potential on the grade. Escalated rear-ender risk on the Arlington platform, but also much-escalated risk of striking a passenger wandering into the platform area (which wouldn't show as a change in signals).
No auto-enforcement because the Green Line fundamentally doesn't have that, so human error has to be factored into the overall risk. This is the highest-risk such spot in the Central Subway. Therefore, there's a hazard red installed to prevent over-speeding...hazard red being the one thing 0.01% of operators won't ignore to their peril like a hazard-yellow. Road analogies: a speed bump, or stop sign or flashing-red flanking both ends of a large hill or low-hanging bridge.
It's not the only hazard red in the subway, or the only one that ever was. There used to be 2 or 3 more of them back when the Central Subway was configured for co-mingled PCC and LRV operation. Extra protection for the weight differential and braking distance differences between the two vehicle types, and reminder to an operator who could be assigned either vehicle type on any given run to remember which braking distance they were dealing with. Those signals all got removed circa 1990 when the dual-running capability got eliminated. And then a new pause got installed in '04 with the North Station relocation at bottom of the Science Park incline inbound. Right at the daylight-to-tunnel transition on that steep grade where operators would be most likely to miss next set of signals protecting North Station Yard if their eyes were still adjusting from blinding sun to the dark.
Archaic? Maybe. "Pointless?" No. Because there is no way to ensure that every operator is going to obey every signal 10,000 times out of 10,000 on a 100% human-controlled operation. When one signal block has been ID'd as a highest-risk spot there aren't many options for closing the risk loophole other than putting in signals that get obeyed without brain fart 100,000 out of 100,000. It's not an ATC-equipped operation; there's no partial- or quasi- ATC patch you can rig up for one single spot while keeping it all-human everywhere else. So what's most likely to accomplish that both with amateurs in cars on a road and professionals in trains in a subway: enforced red.
It's severe, yes. But severe-for-human-nature is all you have to work with when the signals fundamentally aren't capable of overriding the operator. That's not T incompetence. That's dictionary-definition non-ATC ops.
It is quite obvious whenever you enter Kenmore station that there is a type of signal on the Green Line that forces the train to stop, wait 10 seconds pointlessly, and then it switches to green. And then the following signal automatically turns green whenever the block is clear, even though the train is moving at speed on a downslope right into a platform area.
The MBTA is incompetent at running light rail. Period. In this way, and in SO MANY other ways. Boarding, signal priority, signal management, vehicle design, station design, etc, etc, etc.
They're so incompetent that their predecessor public agency the MTA and two-predecessors ago private company BERy had the same exact enforced stops at Arlington and Kenmore. So incompetent that the number of safety pauses has been overall reduced over the years as the vehicles have gotten more advanced.
What is your point in this unfocused rant about all things Green and sucky?
The T commissioned 3 years ago a study on engineering a CBTC system for Green that would give it real enforced signaling. The results said design of such system would be insanely more complicated than originally thought if they wanted a signal system that did not harm headways...like MUNI's new ATC system and SEPTA's new ATC system did on their light rail subways. We'd all be skewering them worse if "fixing the glitch" required running only 70% as many trains. The study rec said much more advance engineering needed to be done before presenting a re-signaling design that would meet the do-no-harm service levels baseline, and to build in years extra lead time on doing that prelim engineering. Because this was an area where Green was legitimately "special" worldwide, being the densest-traffic non-ATC system in the world. They looked at it...didn't shoot first, ask questions later. And committed to giving the engineering re-study years more recommended time to find the right answer. Isn't that a competent move?
Or are we just shouting
"WHARRRGARBL!" and angrily stamping feet because reasons? You can smell all the bullshit you want, but you're checking under the wrong armpit if this specific thing is what's got you all worked up.
