Am aware of the numbers and certainly not saying they're bad. Just not enough to justify a dedicated 6-car underground subway. And if we do extend as 6-car deep bore, a hurdle unto itself, what will end up happening? We'll still be leaving people short. And not just those across the city seeing lines shelved to pay for this expenditure. Even those along the general Sheppard corridor east of McCowan. Malvern area was planned to get subway-like transit 30yrs ago and not even the Fords promised anything there.
Frankly it's a bit silly to be comparing the core downtown area to Sheppard; ditto for comparing B/D, or Eglinton for that matter. Yes there may be problems with the future Crosstown LRT far down the line. But that could've been solved by going with high-floor vehicles and automation with 100m trains. Still wouldn't need anything beyond 100m, so what makes you think such "may not be enough" for Sheppard? Y+E or NYCC are most definitely not Manhattan, nor downtown Toronto for that matter. They're largely transfer points, with significant volumes likely intercepted by a line along Don Mills. I haven't seen even the slightest bit of evidence that something surpassing 20k pphpd would ever be warranted.
*If* in the year 3000 a 4-car, +20k pphpd capacity Line 4 extension turns out to be insufficient for Sheppard, is it a true roadblock? No, because we could build a parallel line somewhere else. Finch, Lawrence, Steeles...we'd have a millennium to plan for it so shouldn't be an issue. And those lines too could be 4-car.
My point is that lines back in the day for the TTC (and transit in North America in general) were always planned with the future in mind -- When the yonge subway opened, you'd often only see a 2 car train running half empty during the off peak, however, they had the foresight (after a few years) to build the platforms to allow for 8 G cars (6-7 H series cars). The same occurred in New York, with platforms being long enough to accommodate 8-10 car 75' long train cars. It may have cost more to construct, but the remodeling costs and pains were never experienced by the daily commuter.
There are certain corridors in the city that don't need subways ever -- Finch is one of them. There are some corridors in the city that need subways now but not to the length of the existing system (Eglinton), and there are corridors in the city that need underground transit but not necessarily a subway (Sheppard). The point is that the city should have some sort of vision in mind and have a network grow along with it.
I'm not even saying Eglinton has to be built with 6 car train platform lengths to begin with, but they should have the ability to extend platforms (like they do with sheppard) to avoid future complications, and to make sure there are zones near subway lines to prevent any sort of utility construction to occur in case of a needed platform expansion in say a century.
They could have built Eglinton much better -- had they cut out half the surface stations, a few underground stations and grade separated the whole thing with TTC subway rolling stock, while only running 2 car trains (that can be coupled). The benefits are -- ease of expansion, lower dwell times, faster transit, more predictable transit on the east side, ability to automate, fleet commonality (ie shared yards with the relief line), better connectivity (many of the stations should have bus terminals, especially in the west and east sides), potential interlining, and most importantly: future proofing. Eglinton as I see it now is being planned in a far too conservative manner. We've seen that traffic along new subway corridors usually doubles within a few years and slowly increases after that (depending on corridor developments and gas prices). 2 car LRV trains with flexities can optimistically carry 150 passengers, realistically, 120 passengers per car, for a total capacity of 300 (240). Since the aboveground section will have limitations of ~ 3-minute frequencies (and turnbacks take up time and can only realistically allow for 2-minute frequencies), we can say that the initial capacity for the section will be 9,000 PPHPD (7,200 PPHPD), for 3 car trains: 13,500 PPHPD (10,800 PPHPD) -- we see greater frequencies (up to a minute and 30 seconds) with the existing streetcars on the KSP and maximum usage of around 4,000PPHPD, so with three cars, at best we'd get 12,000 PPHPD. It says something about how they are building this line.
This is not to say this method of building transit is bad -- Finch and Jane for instance should have LRT lines using flexity trains. Ridership levels on those bus routes are super high, while not being high enough to justify a subway (~40-60K PPD). Compare this to Eglinton -- up to 120K existing PPD along the entire corridor.
