A few points to remember.
The 50 m platforms assisted the design of the SYSTEM in several ways.
- Short platforms were combined with wider 3.0m trains (same as TTC subway).
LRT trains are 2.6m wide (same as MKII SkyTrain).
Narrower trains would require longer platforms and have less internal flexibility for luggage and bikes.
- Short platforms allowed close station spacing at shallow depth while complying with the maximum grade between stations.
Even then, some platforms on the Canada Line have a 0.5% grade - they are not level.
i.e. the station box for Broadway City Hall Station is practically under the pavement at its north end.
Extending the south end by 30m means digging deeper into the hillside, increasing the grade/slope to King Edward Station.
Extending to the north means a deeper station would have been required.
Here's a graphic representation (although I have centred the 50m and longer platforms (measurements not exact)).
Note how the shorter platforms allow a shallower grade - that also means less wear and tear on the vehicles
(Canada is steel on steel for traction, not LIM).
If you have longer platforms, in order to achieve shallower grade between platforms, the tunnels would need to be deep bored.
(i.e. in the above diagram, the platform on the left would have to be deeper)
Deep bored tunnels mean deeper stations / more escalators / longer access times (like the downtown Canada Line stations).
If the Canada Line under Cambie were deep bored, there would be no future station at 33rd Ave. (it would be too deep through Little Mountain rock), King Edward Station would be down more flights of escalators, but there would have been the possibility of a deep station at 16th Ave.
The system as designed with shallow tunnels does not allow a station at 16th Ave. because the grades would be too steep on either side to King Edward and Broadway City Hall.
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