Metro Vancouver Transit Discussion II

[whatnext]

Originally Posted by SFUVancouver

It's been discussed a lot over the years, but the key to the Canada Line's comparatively low cost and fast construction was short platform lengths. The successful bidder aggressively prioritized short platform length and specification of train type, internal configuration, and operational service level program that would fulfil the requirements of the RFP to the letter and nothing more.

With sloping topography along the Vancouver alignment, shorter station platforms let the station boxes and tunnels be built closer to the surface. Shorter platform length permits a station box depth that is just sufficient to let the connecting tunnels maintain a limited grade and smoothly transition from the level station area to a sloping tunnel. A longer platform would require the approaching tunnels to level out earlier. To maintain the gradual transition from level platform area to sloping tunnel to match topography, the station and tunnel would need to be built deeper. Deeper stations means longer construction and more complex engineering. Deeper tunnels necessitate boring, versus the potential for cut-and-cover construction for tunnels closer to the surface. Shallower stations also let people reach platform level or exit the station faster, reducing the total number of people in the station, and, thus, its design capacity and code obligations (e.g. fewer exit stairs, fewer barrier-free shelter-in-place zones, less emergency ventilation, etc.). It is all a virtuous cycle to have small stations close to the surface.

The downside, as we famously know, is that after the RFP contract period expires, which drove all of the fundamental design decisions, one is left with a system for which incremental capacity improvements become more challenging over time. You run trains more frequently, you buy more trains, you modify the interior layout to increase capacity, minimum separation distances may be marginally reduced, you increase train length to the platform maximum, etc. But eventually you are just maxed out with no remaining options.

It's important to keep perspective and recall that all designs have an ultimate system capacity limitation, but they are admittedly more readily apparent when one starts with the foundational constraint of short platforms.

And yet they keep pushing TOD along its route when they know it cannot easily be expanded. I was thinking of how cheap-ass it seems now when I rode to Yaletown recently (1st time in years) and you can see how crowded it was and how they cheaped out on escalators (at every station).