It was quite the opposite when they did the math for Eglinton. Twin bore had less impact than the single bore option, otherwise it probably would have been a single bore as it was the preferred option in every way except massively increased land expropriation/demolition due to compromised foundations.

IIRC, the general rule seemed to be a tunnel width of buffer on either side. So a 10m tunnel needs, roughly, a 30m corridor. The required buffer, of course, varies significantly by soil type with solid rock needing almost no buffer at all.

A civil engineer familiar with downtown Toronto excavations could wrap up this discussion pretty quickly. When Kyle brought it up I thought he might have some training/experience in the area.


The tunnel design contract for the YRL (Yonge Relief Line; my preferred name) left all options on the table:
https://www.merx4.merx.com/public/solicitations/597794367/abstract
I would love to see what those documents contain, but I unfortunately am not a consultant nor willing to pay.
 
Even crazier is Crossrail

https://akshatrathi.com/2014/08/02/...g-a-tunnel-under-london-is-an-epic-endeavour/ (read number 2)

"One of the biggest challenges has been tunnelling under Tottenham Court Road station. It is where the tunnel-boring machine needed to pass through very crowded space. The tunnellers have labelled it “the eye of the needle”. There the 900-tonne tunnel-boring machine has had to pass through a space where 30cm above it was a live escalator and 85 cm underneath was the active Northern Line."

They talked a bit about this in this video. It’s a dry, engineering-oriented video, but pretty neat if you’re into that kind of thing


There’s a lot of other presentations on YouTube about the engineering challenges for Crossrail as well.
 
So we can expect it to open roughly around 2034 then. Great. Sheer idiocy.

Well it’s still anticipated to enter service by 2031, somehow.

2025 is the tentative construction start date. Hopefully “tentative” means “worst possible situation”

It was discussed previously on this forum that this long timeline is likely due to either cashflow issues, or an insufficient local workforce to build the project. Indeed, City staff have mentioned before that they’re concerned that with the amount of simultaneous transit projects in the GTHA, we simply don’t have a workforce large enough to build them all.

The DRL TPAP will begin any moment now, and will wrap up within six months. If it goes anything like prior projects, we should be free to begin tender, detailed design and construction not long after the TPAP is wrapped up.

It took the Crosstown three years to go from proposal to implantation. Hopefully the DRL can emulate that.
 
Well it’s still anticipated to enter service by 2031, somehow.

2025 is the tentative construction start date. Hopefully “tentative” means “worst possible situation”

It was discussed previously on this forum that this long timeline is likely due to either cashflow issues, or an insufficient local workforce to build the project. Indeed, City staff have mentioned before that they’re concerned that with the amount of simultaneous transit projects in the GTHA, we simply don’t have a workforce large enough to build them all.

The DRL TPAP will begin any moment now, and will wrap up within six months. If it goes anything like prior projects, we should be free to begin tender, detailed design and construction not long after the TPAP is wrapped up.

It took the Crosstown three years to go from proposal to implantation. Hopefully the DRL can emulate that.
The TPAP was supposed to start "late 2017", according to the website (reliefline.ca); it has since been changed to "early 2018"
 
My two-cents is that the Spadina Subway Line should be built as an underground LRT line from Bloor down to Queens Quay, where the LRT would continue to Union Station on the existing infrastructure. The Relief Line would continue to the west end (as traditionally planned), intersecting the Spadina Subway at Queen & Spadina.
That's illogical because the TTC streetcars cannot couple together and would only be 1 streetcar in length, effectively making any sort of conversion to LRT useless, plus, where do you store those LRVs? You can't at any TTC streetcar yard because the gauge is different, and the line stops at Bloor. There is literally no room for a yard. Also, the streetcar gives Spadina Avenue its charisma, and it works well with it. Digging a good 20 meters deep (because of PATH) and significantly reducing the stops makes no sense (There'd probably only be stops at Spadina Queen, Dundas, and College, most likely fewer). Build a subway either in-between Bathurst and Spadina (the exits being in the middle, on Spadina, and on Bathurst. It effectively serves both streets as an express option; if you want to go north or east but aren't staying on Spadina, you catch the subway. If you want to go directly down Spadina, take the Spadina car), or down Ossington or Dufferin (especially if you want relief). Also, speaking of smaller trains, they want to make the subway cars on the relief line 4 cars long. Considering that the line is expected to have more PPHPD than the Bloor-Danforth line and the Yonge line, does this not seem shortsighted? The TTC doesn't have to run 6 or 8 car trains during the off-peak, especially if all the entrances to the station's entrances lead to the middle of the platform, but having the platforms built to that length would prevent a future need to lengthen platforms.

Another idea for the relief line... Would the TTC consider using an entirely different rolling stock? With a narrower train than the TRs you can use a single bore tunnel which would bring costs down and maybe funding the whole line more likely.
Then cost of stations go up because longer platforms are needed. Also, does the TTC really need a 7th vehicle type (Bus (all count as one because maintenance isn't as speciallized as rolling stock) , streetcar*2, subway, LRT*2, new Subway car type) in the system? Keep all the subway car dimensions the same, and you won't have problems like Philadelphia, Boston, and New York.
 
That's illogical because the TTC streetcars cannot couple together and would only be 1 streetcar in length, effectively making any sort of conversion to LRT useless, plus, where do you store those LRVs? You can't at any TTC streetcar yard because the gauge is different, and the line stops at Bloor.

Bidirectional rolling stock capable of coupling would need to be purchased specifically for Spadina Line. They'd be stored at current TTC legacy streetcar facilities. The LRVs would be ordered at TTC gauge so it's compatible with the legacy network.

Digging a good 20 meters deep (because of PATH) and significantly reducing the stops makes no sense (There'd probably only be stops at Spadina Queen, Dundas, and College, most likely fewer).

Um, there is no PATH network under Spadina. The mid-block stops would be eliminated, yes. Underground stops would likely be retained at Bloor, Harbord, College, Dundas, Queen, King, and Bremner. Spadina Line LRVs would continue to serve all the existing Queens Quay surface stops and Union Station.
 
Bidirectional rolling stock capable of coupling would need to be purchased specifically for Spadina Line. They'd be stored at current TTC legacy streetcar facilities. The LRVs would be ordered at TTC gauge so it's compatible with the legacy network.



Um, there is no PATH network under Spadina. The mid-block stops would be eliminated, yes. Underground stops would likely be retained at Bloor, Harbord, College, Dundas, Queen, King, and Bremner. Spadina Line LRVs would continue to serve all the existing Queens Quay surface stops and Union Station.

IDK why I said PATH so you can laugh at me there. And again, is it really worth adding another set of LRV types (we already have 4 either here or coming (Flexity Freedom, Flexity Outlook, CLRV (Being retired), ALRV, Citadis), possibly 5 depending on the streetcar expansion). Also, the platforms would be so long on Spadina that local service is effectively killed, or speed of service is basically non-existent. If you're going to build underground, especially in downtown Toronto, and really all urban areas, build it as a subway to facilitate future demand. If you're going to build aboveground, build it as an LRT to densify the surroundings.
 
That's illogical because the TTC streetcars cannot couple together and would only be 1 streetcar in length,

Not true, the TTC Outlooks, like any other Flexity product, do have couplers and can run coupled. In fact, since they have single ended cabs you'd get extra capacity. Here's a video:

 
IDK why I said PATH so you can laugh at me there. And again, is it really worth adding another set of LRV types (we already have 4 either here or coming (Flexity Freedom, Flexity Outlook, CLRV (Being retired), ALRV, Citadis), possibly 5 depending on the streetcar expansion).

Given the high ridership demands on the 510, I believe it's worth consideration. The 510 is the fifth busiest route on the TTC network, moving 55,000 people daily; it's busier than any bus route, and has more daily riders than the Sheppard Line, SRT and the Scarborough Subway.

Ridership on the TTC streetcar network is expected to skyrocket in the coming years, and this ridership increase will be exceptionally pronounced on the 510 Line, as it runs through King and Spadina, which is Canada's fastest growing neighbourhood. The population of that neighbourhood will increase 2.5x by 2031. The LFLVs can theoretically boost the capacity of the 510 by 1.75x, to around 96,000 daily riders, and I expect that most, if not all, of that new capacity will be saturated by high passenger demand.

To put things in perspective, the Eglinton Crosstown Line is expected to have 180,000 daily riders to 2031. Given the "natural" ridership increases the 510 will experience due to densification at King/Spadina, and given the number of riders that would be diverted from the University Line, it is completely conceivable that ridership on a Spadina subway line would exceed the daily ridership of the Eglinton Crosstown (however, I would expect peak hour demands to be lower on Spadina, since its ridership is more evenly distributed over 24 hours).

Furthermore, with the potential for long term capacity constrains on the University Line (I'm talking 2030s to 2040s timeframe), something will need to be done to relieve demand on that line, and a subway on Spadina is the most obvious solution.

If the price to achieve this includes buying LRVs specifically for Spadina, it's worth it. The SRT has had unique rolling stock for 40 years, and its ridership is a small fraction of a potential Spadina subway.

Finally, I'll emphasize that I'm not saying this is something that should be considered today. This would be a project for the distant future, probably not until the 2030s decade.
 
Not true, the TTC Outlooks, like any other Flexity product, do have couplers and can run coupled. In fact, since they have single ended cabs you'd get extra capacity. Here's a video:


It can't run coupled in revenue service. Any coupling is restricted to towing for maintenance purposes. But this doesn't necessarily preclude modifying the LFLRVs to enable them to provide revenue service while coupled.
 
It can't run coupled in revenue service. Any coupling is restricted to towing for maintenance purposes. But this doesn't necessarily preclude modifying the LFLRVs to enable them to provide revenue service while coupled.

What's the technical restriction on revenue service? Assuming the Outlooks are built more or less from the same parts bin as other Flexities, wouldn't they have to go out of their way to break that functionality?

Obviously there's an operational issue, the line itself would need rebuilding for 2 car operation, but was wondering what problem the trains themselves would have.
 

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