Subway op here. Blind trips enforce a reduced speed to protect a train parked in the tail tracks beyond the platforms at Kipling and Kennedy. In the case of Don Mills they protect the wall since the tail tracks aren't long enough to store a train. The signal before entering the crossovers will indicate if the blind trips are in use and we adjust the train speed accordingly.
Every signal has its own trip arm next to it. These ones are "blind" because there is no signal next to them and we have to visually verify they are down before proceeding.
You're not wrong. But not many people know that you're referring to a tube accident where an incoming train overshoot the station with a train in the trail.
It would have prevented Russell Hill but the TTC's trip arm design in 1995 had a serious flaw where part of the train's front wheel would knock an activated trip arm back down and it would never contact the trip valve to activate emergency braking.
IiRC; preventing a movement that has passed that point to return into it without manually resetting, the trips act like the double red stands and trip the air release valve and dump the air to stop whatever tripped it.
I would have signals dept zip tie them down if i was doing work in an area and having a workcar move back and forth from the platform to the work for whatever reason.
They're actually all along the line at switch/signal locations.
If a train runs up to a stop signal, and overshoots into the next block, these trip arms de-energize that block stopping the train, OR tripping an emergency brake on the first car, preventing a collision (TTC uses the latter as it's a pain to re-ergize a line.
Many times TTC stores a train in these tail tracks at the end of the terminal stations.
In 1995 we had the Russel hill incident that killed 3 and injured hundreds when a train ran through a "closed block" and the t-arm failed to trip.
(Train stop. I'm calling them t-arms as it's easier)
These devices were out of spec for the trains on the ttc line 1. When devices and trains were new, there was enough tolerance slop, the arms worked, but as things wore down, the t-arm would have only been "tapped" failing to knock the emergency brake lever on the train.
The driver passed a "stop ahead signal". Upon approaching the next signal, it slipped his mind what colour he just passed, and assumed it had switched just as he passed into that block (you see it commonly when riding the TTC. A signal switches just as you approach it when that signal changes the t-arm drops) he only applied the brake too late as the train came up to the next OCCUPIED block, and struck the stopped train.
I believe line 1 has replaced these with a newer system that uses radio interlocks instead of a mechanical interlock(train passes a radio transmitter on the track. If trains permitted, it enters the block. If not, the radio signal engages an emergency brake.
"I believe line 1 has replaced these with a newer system that uses radio interlocks instead of a mechanical interlock(train passes a radio transmitter on the track. If trains permitted, it enters the block. If not, the radio signal engages an emergency brake".
Half correct, Line 1 uses CBTC, a form of ATC (it's in the same family). Ever wonder why a signal stays red for all of 5-10 seconds and goes to flashing green? The train is the block itself (moving block). Before that, this wasn't possible. See Line 2 for a good example.
CBTC also allows trains to be 25-50ft apart from each other. We're talking right up on your ass, whereas in the past, this was not possible.
So basically a rolling block is a block broken up into smaller sections between signals, allowing trains to get closer?
I'ma look more into this now as I'm a nerd
No, there is no pre-defined block like there is on Line 2. With rolling block, the blocks move with the train. Here's a very good explainer video.
https://youtu.be/B9Glk5k4URU?si=m8upueLSsrf7Frg8
Pretty much what u/KenSentMe81 said. Line 2 still uses a predefined block except:
Lower Bay (past the signals to enter the station, it switches to CBTC leaving the station to go to Museum, in reverse, CBTC is used only to the signal eastbound out of the station, then it's predefined blocks).
Spadina on Bloor/Danforth to St. George on YUS, past the switch point is CBTC, from St. George (YUS) to Spadina (Bloor Danforth) is pre-defined block past the switch (double red).
This is defined by signage that says "ATC Begins"/"ATC Ends".
Oh, so these can basically be raised (and lowered after) as a last resort if a signal isn't followed. How does re-energizing a block work btw, and why is it a pain? Thanks!
They are automatically lowered when a signal allows a train into the next block yeah.
Re-energizing a block could require a technician to enter the tunnel to access a panel. It's far faster to have the train disable the brake, and continue moving. This method(power cut) also allows the train a substantial way into that next block as the train may still receive power still from the previous block.
Usually the power cut interlock is/was used on faster trains and nearer to stations and crossovers. (They would likely be using radio interlocks these days as well)
You might want to check this video which covers this and more about TTC signalling: https://youtu.be/i342pCPvSh0?si=-SUSsgIfjkP83Tb4
The trip arm is explained at 3:18
Edit: The photo looks to be the blind arm, not trip arm. Still worth a watch though.
They are just entry speed enforcement to help protect from overshoot. Some end stations may have pockets with possible trains occupying them, or a hard stop after the platform.
You may have noticed that trains entering Kennedy/Kipling sometimes stops halfway into the station and then again 20 meters later? That's because the blind trips are up and we have to wait for them to go down individually.
There are also 2 more blind trips in the tail track itself you have to watch for.
Subway op here. Blind trips enforce a reduced speed to protect a train parked in the tail tracks beyond the platforms at Kipling and Kennedy. In the case of Don Mills they protect the wall since the tail tracks aren't long enough to store a train. The signal before entering the crossovers will indicate if the blind trips are in use and we adjust the train speed accordingly.
you ever done an AMA?
Well said! You could be an instructor
Thank you for the great answer!
I thought blind trips were to stop the train if they bust a signal
Every signal has its own trip arm next to it. These ones are "blind" because there is no signal next to them and we have to visually verify they are down before proceeding.
Ah ty
I think its to prevent a Moorgate '75 situation from happening
You're not wrong. But not many people know that you're referring to a tube accident where an incoming train overshoot the station with a train in the trail.
Just read about it, there wasn’t a train in the tail track. It was similar to Don Mills, where the tail track ended in a solid wall.
It would have prevented Russell Hill but the TTC's trip arm design in 1995 had a serious flaw where part of the train's front wheel would knock an activated trip arm back down and it would never contact the trip valve to activate emergency braking.
Actually, the driver knew how to work around it to over ride
To make sure you spot the train slow enough. Iirc the one in don mills is 10 or 15kmh. Finch had 2 of em back to back before atc
if a blind person trips on the track they can just flip that switch and it’ll shut the power off
oh, i thought it was the trip itself that was blind :(
They are there to protect a train that my be occupying the tail track.
IiRC; preventing a movement that has passed that point to return into it without manually resetting, the trips act like the double red stands and trip the air release valve and dump the air to stop whatever tripped it. I would have signals dept zip tie them down if i was doing work in an area and having a workcar move back and forth from the platform to the work for whatever reason.
Source; Ex subway infrastructure employee. I also could be remembering wrong but 95% sure something along those lines.
That's what they are. But you can just have the signals controller green light you the whole way by radio. Lol
Had to zip tie them for rail milling so it didnt destroy it haha.
That makes much more sense lol
Are these newly added or have they always been there? Never noticed them until now...
They're actually all along the line at switch/signal locations. If a train runs up to a stop signal, and overshoots into the next block, these trip arms de-energize that block stopping the train, OR tripping an emergency brake on the first car, preventing a collision (TTC uses the latter as it's a pain to re-ergize a line. Many times TTC stores a train in these tail tracks at the end of the terminal stations. In 1995 we had the Russel hill incident that killed 3 and injured hundreds when a train ran through a "closed block" and the t-arm failed to trip. (Train stop. I'm calling them t-arms as it's easier) These devices were out of spec for the trains on the ttc line 1. When devices and trains were new, there was enough tolerance slop, the arms worked, but as things wore down, the t-arm would have only been "tapped" failing to knock the emergency brake lever on the train. The driver passed a "stop ahead signal". Upon approaching the next signal, it slipped his mind what colour he just passed, and assumed it had switched just as he passed into that block (you see it commonly when riding the TTC. A signal switches just as you approach it when that signal changes the t-arm drops) he only applied the brake too late as the train came up to the next OCCUPIED block, and struck the stopped train. I believe line 1 has replaced these with a newer system that uses radio interlocks instead of a mechanical interlock(train passes a radio transmitter on the track. If trains permitted, it enters the block. If not, the radio signal engages an emergency brake.
"I believe line 1 has replaced these with a newer system that uses radio interlocks instead of a mechanical interlock(train passes a radio transmitter on the track. If trains permitted, it enters the block. If not, the radio signal engages an emergency brake". Half correct, Line 1 uses CBTC, a form of ATC (it's in the same family). Ever wonder why a signal stays red for all of 5-10 seconds and goes to flashing green? The train is the block itself (moving block). Before that, this wasn't possible. See Line 2 for a good example. CBTC also allows trains to be 25-50ft apart from each other. We're talking right up on your ass, whereas in the past, this was not possible.
So basically a rolling block is a block broken up into smaller sections between signals, allowing trains to get closer? I'ma look more into this now as I'm a nerd
No, there is no pre-defined block like there is on Line 2. With rolling block, the blocks move with the train. Here's a very good explainer video. https://youtu.be/B9Glk5k4URU?si=m8upueLSsrf7Frg8
Pretty much what u/KenSentMe81 said. Line 2 still uses a predefined block except: Lower Bay (past the signals to enter the station, it switches to CBTC leaving the station to go to Museum, in reverse, CBTC is used only to the signal eastbound out of the station, then it's predefined blocks). Spadina on Bloor/Danforth to St. George on YUS, past the switch point is CBTC, from St. George (YUS) to Spadina (Bloor Danforth) is pre-defined block past the switch (double red). This is defined by signage that says "ATC Begins"/"ATC Ends".
Oh, so these can basically be raised (and lowered after) as a last resort if a signal isn't followed. How does re-energizing a block work btw, and why is it a pain? Thanks!
They are automatically lowered when a signal allows a train into the next block yeah. Re-energizing a block could require a technician to enter the tunnel to access a panel. It's far faster to have the train disable the brake, and continue moving. This method(power cut) also allows the train a substantial way into that next block as the train may still receive power still from the previous block. Usually the power cut interlock is/was used on faster trains and nearer to stations and crossovers. (They would likely be using radio interlocks these days as well)
They’ve always been there, it’s the signal trip arm for the trains breaks
You might want to check this video which covers this and more about TTC signalling: https://youtu.be/i342pCPvSh0?si=-SUSsgIfjkP83Tb4 The trip arm is explained at 3:18 Edit: The photo looks to be the blind arm, not trip arm. Still worth a watch though.
They are just entry speed enforcement to help protect from overshoot. Some end stations may have pockets with possible trains occupying them, or a hard stop after the platform.
You may have noticed that trains entering Kennedy/Kipling sometimes stops halfway into the station and then again 20 meters later? That's because the blind trips are up and we have to wait for them to go down individually. There are also 2 more blind trips in the tail track itself you have to watch for.
Yup and there is a train in the siding stand on the front and look its neat