Two Questions on the Green Lines

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Two Questions on the Green Lines

Postby gprimr1 » Mon Jul 29, 2013 7:40 pm

I'm attending a conference in Boston this week and I have a couple questions on the Green Line.

1.) Why does the train stop (either rolling stop or full stop) before entering each underground station?

2.) Why is there no "A" route?
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Re: Two Questions on the Green Lines

Postby Adams_Umass_Boston » Mon Jul 29, 2013 7:47 pm

There was an A line.
http://en.wikipedia.org/wiki/Green_Line_%22A%22_Branch

But it is sadly gone :(
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Re: Two Questions on the Green Lines

Postby The EGE » Mon Jul 29, 2013 8:14 pm

As Adams said, there used to be an A branch. The Green Line is the remains of a once-huge network of trolley lines which fed into the Tremont Street Subway. Of the 5 lines that survived to the letter scheme introduced in 1967, the A Branch was cut in 1969 and the outer half of the E in 1985.

The Green Line uses an ancient signalling system; other can provide more details, but in short it's not advanced enough to know for sure whether there's a car already in the station. So the car must slow and the driver checks.
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Re: Two Questions on the Green Lines

Postby jrc520 » Mon Jul 29, 2013 8:57 pm

Ok, So, the signalling system does know that there is a car in the station. For safety, you have to stop before entering the station when there is another car. The signal is Yellow over Yellow, which is basically a "Stop, look, determine if you can fit" signal. If there is no car, it will either be yellow or green.
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Re: Two Questions on the Green Lines

Postby boblothrope » Tue Jul 30, 2013 11:03 am

jrc520 wrote:Ok, So, the signalling system does know that there is a car in the station. For safety, you have to stop before entering the station when there is another car. The signal is Yellow over Yellow, which is basically a "Stop, look, determine if you can fit" signal. If there is no car, it will either be yellow or green.


In a few places, trains always have to stop before proceeding, even if the block ahead is unoccupied.

There's an extended discussion here, with several theories about why this is necessary: viewtopic.php?f=65&t=150924
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Re: Two Questions on the Green Lines

Postby gprimr1 » Tue Jul 30, 2013 11:15 am

I got a front seat today and was able to see just how many signals are in those tunnels.
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Re: Two Questions on the Green Lines

Postby Gerry6309 » Thu Aug 01, 2013 3:09 pm

gprimr1 wrote:I got a front seat today and was able to see just how many signals are in those tunnels.

The signal system was added to the Green Line when heavier cars came into general use alongside the original wooden ones. Part of it dates to the Rapid Transit (Orange Line) operation from 1901 to 1908. It was designed for cars with a top speed of 25mph (downhill with a tailwind) which was all that existed prior to 1941. Time lights arrived when PCCs (42mph) started sharing the tunnels with the older equipment. The PCCs were later cut to about 25mph by eliminating field shunting, so since the LRVs arrived, followed by Type 7 and 8 cars, the cars exceed the design speed of the signals regularly, resulting in lengthy stops at some time signals. The cars encourage the speed, and as a result there are more stops, and occasional rear-enders.
Gerry. STM/BSRA

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Re: Two Questions on the Green Lines

Postby CRail » Thu Aug 08, 2013 1:56 am

The EGE wrote:The Green Line uses an ancient signalling system; other can provide more details, but in short it's not advanced enough to know for sure whether there's a car already in the station. So the car must slow and the driver checks.

This is blatantly untrue. The signal system positively detects the presence or absence of a car within any circuit. Safety stops have nothing to do with 'uncertainty' of block occupation by the system.

Perhaps what you're referring to is the double yellow, which only exists at station entrances. Most central subway stations are made up of two blocks. If only the farthest block is occupied, the signal will show a permissive double yellow indication (which is to be treated as a stop and proceed). This tells the motorman that the station is occupied, but there's enough room on the platform for one more train or car. Now with the ADA and other considerations, they want all trains to board at the same location (hence all the "First Car Stop Here" signs), so trains will often wait outside the station until the first train starts to clear it.
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Re: Two Questions on the Green Lines

Postby gprimr1 » Thu Aug 08, 2013 9:33 am

Those were the most annoying stops, those right outside the station ones.
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Re: Two Questions on the Green Lines

Postby Rbts Stn » Thu Aug 08, 2013 2:55 pm

gprimr1 wrote:Those were the most annoying stops, those right outside the station ones.


No, the most annoying ones are INSIDE the station, but not opening the doors until you get up to the First Car Stop Here sign. Everyone on the train surges towards the doors, everyone on the platform does the same, and then they have to sashay down the track while the train creeps ahead.
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Re: Two Questions on the Green Lines

Postby The EGE » Thu Aug 08, 2013 6:04 pm

CRail, thanks for the corrections.
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Re: Two Questions on the Green Lines

Postby gprimr1 » Thu Aug 08, 2013 7:09 pm

-Greg Primrose
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Re: Two Questions on the Green Lines

Postby diburning » Fri Aug 09, 2013 2:42 pm

Rbts Stn wrote:
gprimr1 wrote:Those were the most annoying stops, those right outside the station ones.


No, the most annoying ones are INSIDE the station, but not opening the doors until you get up to the First Car Stop Here sign. Everyone on the train surges towards the doors, everyone on the platform does the same, and then they have to sashay down the track while the train creeps ahead.


What's even more annoying is at Government Center outbound when most operators don't pull up to that First Car Stop Here sign and load from the second car position while some pull all the way up. It makes it a ridiculous mad dash for everyone on the platform.
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Re: Two Questions on the Green Lines

Postby SM89 » Fri Aug 09, 2013 3:40 pm

diburning wrote:
What's even more annoying is at Government Center outbound when most operators don't pull up to that First Car Stop Here sign and load from the second car position while some pull all the way up. It makes it a ridiculous mad dash for everyone on the platform.


It's similar at Prudential. They are supposed to pull way up because that's where the escalator and sign are, but a lot of the times they stop half way down the platform because that's where people come down the stairs and wait, except for me of course...
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Re: Two Questions on the Green Lines

Postby BostonUrbEx » Fri Aug 09, 2013 6:18 pm

diburning wrote:
Rbts Stn wrote:
gprimr1 wrote:Those were the most annoying stops, those right outside the station ones.


No, the most annoying ones are INSIDE the station, but not opening the doors until you get up to the First Car Stop Here sign. Everyone on the train surges towards the doors, everyone on the platform does the same, and then they have to sashay down the track while the train creeps ahead.


What's even more annoying is at Government Center outbound when most operators don't pull up to that First Car Stop Here sign and load from the second car position while some pull all the way up. It makes it a ridiculous mad dash for everyone on the platform.


Usually, GC terminating trains will only pull up to the escalator, so everyone can filter out easily. Trains going to North Station or Lechmere pull all the way to the end.
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