LFs are often hyped as having some magical properties like being silent and invisible and making a streetscape amazing by their very existence. And it feels like it was in large part a 'vibes' decision, even though the benefits of LF won't be particularly well realized for a huge portion of the total line, including pretty much everything contemplated to date in the initial phasing.
LF makes sense (if not damn near a necessity) for an at-grade Centre St alignment from the Bow River to Beddington. But that would have really been just 16th to Beddington (6 stations, 7.6km) in the original plan. For the 4-6 underground stations originally conceived, HF would be pretty obviously better from an excavation standpoint. North of Beddington and south of the core it seems like a pretty marginal difference...a few stations might benefit a bit from being LF, though HF would be faster for stations that are spaced out...either would be fine.
So one could argue that 7.6kms are dictating all 46km. Which was probably fine...until we run into our present circumstance of needing some drastic changes, but we've painted ourselves into a corner. Which isn't to say that HF would magically solve anything, but it could have meant some more options for creative solutions (if the city showed an inclination to do so).
Low floor LRVs are not magical. But neither are high floor trains. There are two key aspects to choosing low floor trains. The first is that they are the industry standard, and have been for almost a quarter century. Every single LRT system in Canada - Calgary, Edmonton, Ottawa, Waterloo, Toronto, Mississauga and Quebec City all picked low floor over high floor. As have Seattle, Portland, Denver, Salt Lake City, Los Angeles, Phoenix, Denver, Houston, Dallas, and so on. As have Bergen, Tampere, Porto, Utrecht, Granada, Madrid, Malaga and more. As have Sydney, Adelaide, Melbourne, Gold Coast, etc. As have Kaohsiung, Shenyang, Addis Ababa, Casablanca, Tunis, Rio de Janeiro, Medellin and others. There are basically only two types of light rail lines: those run by agencies that have picked low floor over high floor, and those that were built when only high floor trains were available.
Light rail trains are always built to order, and it's easier to adapt a low floor design to high floor than vice versa, but there is no benefit to the city in locking in new lines to legacy infrastructure technology, in the same way that it wouldn't make sense to buy buses with manual transmissions, or coin-only ticket vending machines. It's the industry standard technology, and there are more bidders and less design/customization work to order low floor vehicles. High floor doesn't give you a single thing that low floor trains don't.
And the second is that you want:
1). the floor of the train to be at the same level as the platform edge, which provides for safer and faster boarding, and supports people using wheelchairs, scooters, bikes, walkers, people with limited mobility, people with daschunds, basically everybody.
2). the sidewalk to be at the same level as the building door, which again provides for safe and universal access to buildings.
Given 1 and 2, if there is a substantial difference in the height of the sidewalk/buildings and the height of the platform/train floor, that adds spatial conflict. If they are both at roughly the same height, then there is no space needed for transition, and the space is maximally useful (it can function as a wide sidewalk at noon when people are going to lunch, and a wide platform at rush hour; people who need more space (e.g. wheelchair users, people hoiding hands) have more room to maneuver. If not, then you need not only a sidewalk and platform big enough to hold demand individually, but also space for transition between the two, which means at least some ramps, which take a lot of space.
For a suburban station built on a lot of land (like most of the SE stations), it doesn't much matter the difference between low and high floor -- a little more concrete and a little more space, but nothing major. For a station in an urban context near buildings -- the actual places people taking the train want to get to -- then low floor has a huge advantage in that platforms can more-or-less serve as sidewalks.
A big question I've never seen pondered is what happens after build out if N vs SE have significantly unbalanced ridership. Personally, I'm very bullish on the north and bearish on the SE. What if we get to a point where Centre St is overloading 2 car trains and either needs higher frequency and/or more cars? But the SE doesn't need either? North would be 10-12 stations, 15-18kms. But then would we have to extend another 16 stations to the SE? Or run higher than necessary frequencies for that 28 kms?
We already have unbalanced demand in the existing LRT lines, especially the northeast vs the west parts of the Blue Line, which some years ago were 2:1 in terms of ridership (the red line was 1.6:1 for the south vs the northwest). The answer is to run better service for some segments than they theoretically deserve. This is particularly less of an issue with the Green Line being a separate right of way, so it's not having to take away space from other lines. Even a low ridership LRT trip is still a ton of people to be transported by one driver. Part of the point of LRT is that the capital costs are high, but you get really cheap per-rider operating costs. Even the equivalent of 10 people rattling around on an existing LRT car is still 30 people per train, which is full seated capacity for a bus.
It is operationally possible (depending on very specific details of the line) to short turn some trains, every second southbound train could in theory turn back at say Ramsay (if the trains are at say 5+ minutes headway). But it's really not that useful; you don't save that much by not running a train for an extra 15 minutes to the end of the line, and it makes everything more complex.
