Green Line LRT | ?m | ?s | Calgary Transit

[darwink]

whereas here, you are essentially going down 2/3 storeys to reach to station.

It depends how you design the stations. no need for a mezzanine if you take a bit more surface land.

Totally possible to build a station this deep as an 'underground' station. You do end up in an optimization problem though: if you go deeper you can build the station box far less strong with some nice arches. But then your access solution is likely more expensive. Which is better? Don't know.

 

[Red Star]

If both blue/red were buried and interlined then we wouldn't want to add green to the mix. It would theoretically open 7th open for a surface running green line, but I doubt that would be any more popular in this alternate reality.

A buried line almost certainly would have meant fewer DT stations - which would be net positive today, but I think it would have been detrimental in building up the ridership. The train speed benefits of being UG would have been a lot lower for the first ~20 years (less traffic and lower train frequencies). 500m station spacing plus a couple flights of stairs/escalators would have made it less competitive for a lot of people who enjoyed hopping off within 2-3 blocks of their office.

Today, adding stairs and an extra block or two to cover on foot wouldn't net out much slower for the few people who have to travel further, while making the system much faster for everyone else.

Why not? The BART system in SF has 4 lines sharing a tunnel under Market St..

I'm sure three LRT lines can share one tunnel without effecting operations too much. Plus, the SE LRT will only operate at 10 minute headways during rush hour.

 

[trtcttc]

It depends how you design the stations. no need for a mezzanine if you take a bit more surface land.

Totally possible to build a station this deep as an 'underground' station. You do end up in an optimization problem though: if you go deeper you can build the station box far less strong with some nice arches. But then your access solution is likely more expensive. Which is better? Don't know.
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It seems like these shallow stations were much more common a few decades ago, but modern stations seem to be much deeper. Is that just many cities are building stations that are way too large or is there other reasons why we have to dig deeper with all the surrounding infrastructure that's in place now. I don't know the answer but there's buildings with much larger foundations now and other infrastructure surrounding it.

 

[lemongrab]

It seems like these shallow stations were much more common a few decades ago, but modern stations seem to be much deeper. Is that just many cities are building stations that are way too large or is there other reasons why we have to dig deeper with all the surrounding infrastructure that's in place now. I don't know the answer but there's buildings with much larger foundations now and other infrastructure surrounding it.

How many cities are building their 'first' subway tunnel? Could it be that most cities are just having to go under other subways?

I've never had the impression that 8 Ave subway will be particularly deep. But darwink's photo raises a thought for my idea - you could do a shallow trenched station between 7th and 8th (north side could blend gradually into Century Gardens), letting you stay under 8th before doing a double transition to fly over 7th Ave and beyond (just 260m to do this which gains 10.4M at 4% - very tight, but maybe not impossible).

If the subway were to stay UG the whole way, I wonder if it would need to run up 8 St SW instead of 9th? That would give a lot more space (through 'ParkPlus Lot 6' near Joe's Bike Repair trailer) to transition and tie in to the bridge over the Bow.

 

[lemongrab]

Why not? The BART system in SF has 4 lines sharing a tunnel under Market St..

I'm sure three LRT lines can share one tunnel without effecting operations too much. Plus, the SE LRT will only operate at 10 minute headways during rush hour.

Trade offs with each option. I would think a full optimized single line at surface could perform about the same as a busy interlined subway (especially if you factor the time spent on stairs/escalators).

But a single line underground could fly, and you'd have no extra system resiliency issues. Remember it's not just an EB red train competing with EB blue train for space, that EB red train may have to wait for a WB blue train (or vice versa) to get on to the interline (same thing on east side of DT). That problem multiplies with every line you add.

 

[ByeByeBaby]

I respectfully disagree with the first part.

If the downtown LRT Subway was built below 7th or 8th Ave from day 1, it would have been so easy to tie the SE LRT into the existing system. Now the SE LRT is delayed by 11 years, and the planners still don't have a definite plan on how to route the line through downtown.

If the downtown LRT was built as a subway from day 1, I 100% guarantee we wouldn't have any problems with the SE LRT today.

Because we wouldn't be anywhere near building a fifth line, we'd be building the extensions to McKnight and Dalhousie, and doing engagement on the West LRT.

Why not? The BART system in SF has 4 lines sharing a tunnel under Market St..

I'm sure three LRT lines can share one tunnel without effecting operations too much. Plus, the SE LRT will only operate at 10 minute headways during rush hour.

It doesn't matter how many colours are on the map. BART lines have much lower frequency; three of the four lines are 20 minute headways and the yellow is 10 minutes. Put all together, the Transbay Tunnel handles about 15 trains per hour per direction at peak.

Running three lines each "only operating at 10 minute headways" is 18 trains per hour. Running two at five and one at 10 is 30 trains per hour, which is theoretically possible but would be a terrible operating condition -- no room for error and no ability to expand.

 

[badc0ffee]

BART seems to work pretty well (or maybe I've been lucky), but the Muni lines carried by the upper two tracks of the Market Street tunnel are subject to bunching and delays all the time. SF might use the same S200 cars as us, but their system is slower, less used and more barebones.

 

[trtcttc]

If the downtown LRT was built as a subway from day 1, I 100% guarantee we wouldn't have any problems with the SE LRT today.

Because we wouldn't be anywhere near building a fifth line, we'd be building the extensions to McKnight and Dalhousie, and doing engagement on the West LRT.


It doesn't matter how many colours are on the map. BART lines have much lower frequency; three of the four lines are 20 minute headways and the yellow is 10 minutes. Put all together, the Transbay Tunnel handles about 15 trains per hour per direction at peak.

Running three lines each "only operating at 10 minute headways" is 18 trains per hour. Running two at five and one at 10 is 30 trains per hour, which is theoretically possible but would be a terrible operating condition -- no room for error and no ability to expand.

30-33 is the realistic maximum for a ATC train line. And it’s worse if it’s 3 different lines because it’s more difficult to plan for headway, that they will have to hold for spacing or cannot run that many trains.

How many cities are building their 'first' subway tunnel? Could it be that most cities are just having to go under other subways?

I've never had the impression that 8 Ave subway will be particularly deep. But darwink's photo raises a thought for my idea - you could do a shallow trenched station between 7th and 8th (north side could blend gradually into Century Gardens), letting you stay under 8th before doing a double transition to fly over 7th Ave and beyond (just 260m to do this which gains 10.4M at 4% - very tight, but maybe not impossible).

If the subway were to stay UG the whole way, I wonder if it would need to run up 8 St SW instead of 9th? That would give a lot more space (through 'ParkPlus Lot 6' near Joe's Bike Repair trailer) to transition and tie in to the bridge over the Bow.

No it’s not tunneling underneath. The TTC for example, the downtown trains are actually fairly shallow, built in the 50s. But the newer TYSSE extension to Vaughn Metropolitan Centre (Green field land, going under roads and highways) is significantly deeper. The station boxes are also way over built but that one I think is easy to correct, but not sure why they dug so deep.

 

[CalgaryTiger]

If you do a Stephen Ave cut and cover you don’t need to go deep at all. Stephen Ave itself would act as a pretty good crossover between lines. Too bad they’re redoing all the utilities under it now but at least they know where the utilities are. It’s too bad we took so long to get the Green Line to this point… if the Green Line were open now, at least part of it, I think planners would’ve been looking at a Stephen Ave subway as a real possibility. Instead, we’re still figuring out the Green Line and Stephen Ave is being redone and likely won’t be touched for 30 years because everything was just redone. Who knows, maybe the placement of the new utilities makes a shallow bore realistic?