I feel like I'm being misinterpreted here, and I didn't mean to send the topic in a wrong direction so I'll just close with the clarification that I wasn't advocating the Vancouver system should - or could - be "hub and spoke." I simply explained that the DC system was, in the context of that actually causing one of the problems they now face (I might add ; ). While DC doesn't have mountains, it does have several rivers over and under which the system did have to be constructed. There were also bureaucratic and political hurdles of dealing with 2 different states, the local district government and the federal government so there had to be plenty of negotiating and compromise along the way (which can be just as daunting as a physical mountain

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The point I would like to make clear, though, is I don't see how having different technologies and cars is cost-effective in the long-run. It may be too far along to rectify at this point, but clearly there are advantages across the board (maintenance efficiencies, purchasing efficiencies, manpower training, etc, etc) if you have a system that uses one technology and cars that can be transferred to other lines for capacity smoothing, etc. Even during the time I lived in DC, the metro authority shifted car configurations among the various lines as population and demographic shifts occurred (and as some lines expanded, changing the transportation patterns within the system). Also, as new cars were ordered and arrived, the metro authority was able to provide new cars to increase capacity on the lines that needed them most to ensure they could handle the capacity.
It just seems when you use different technology and different cars for different segments or lines, you are setting yourselves up with increased costs for the lifetime of the system. Whatever money you might be saving up front (if any), I expect you would lose having to maintain and supply the disparate systems for the duration.
The last point I want to re-emphasize is the capacity issue that has dominated the discussion here. What kind of planning creates a system that from day one has no growth potential without additional massive spending (extending platform lengths, etc)? What I was trying to point out was that the DC system was built so that stations built 30+ years ago are just now beginning to approach their full capacity. When started, many of the trains were 2 or 4 car-length trains. Just during the time I lived in DC, they went from 6 to 8-car length trains on the lines during peak times, and those extended trains fit in the originally constructed station platforms. Without a doubt, it must have cost more upfront to construct the stations with the larger platforms and larger entrance systems. But as the capacity has grown, a great deal of money has been saved from the core system, meaning funds could instead by applied to expanding the system network to reach more communities and neighborhoods.
I am excited about the Canada Line, and I think the transportation system here in Vancouver is enviable in many ways. I'm just pointing out my own observations those things that do strike me as odd, having moved here from a city that had a very good planning process and a system that used a common technology and interchangeable rail cars.
As excited as I am by the sleek look of the new Canada Line cars, a little voice in my head still goes, "Why a new car? Shouldn't all the lines use the same cars?" And it does seem strange to me that the new line is built with (seemingly) little forethought into what will be necessary when the capacity needs to be expanded. Are there other ways of expanding the capacity that have been discussed (more runs on the same line, etc?). Perhaps I'm just not getting the full picture from what I have read.
Those were my main points - I should have just stuck to them. I certainly didn't mean to be perceived as attacking the system here. I like it, and use it, and am absolutely thrilled by the new line being constructed. Will be so happy when it is done, as I'll probably use it more than any of the existing lines.