https://dailyhive.com/vancouver/montreal-rem-vancouver-skytrain-comparison
https://en.wikipedia.org/wiki/R%C3%A9seau_express_m%C3%A9tropolitain#Main_line
If the SkyTrain could ever have significantly longer stations & longer trains, then it might become on a similar capacity level as the Montreal Metro. Indeed, the SkyTrain should not only be significantly longer that the REM train, but eventually as long as a Montreal Metro train.
The first 2 SkyTrain lines should have had stations that could eventually accommodate 10 car trains. The slightly upgraded stations will only be able to accommodate the newest 5 car trains, not 10 or even 8 cars.
https://en.wikipedia.org/wiki/Alstom_Metropolis_Saint-Laurent#Comparison_with_Montreal_Metro_trains
The YVR-Canada_Line should have been started with 5 car trains, but the stations were only designed to accommodate a 2.5 car joke of a train. The absurdly short stations are only 50 m and don't have enough level clearance to become 100 m, especially not 150 m. Its a fine example of how Vancouver just can't seem to properly plan for growing infrastructure demands. The Montreal Metro has stations that are 152.5 m (500'), which can accommodate 9 car trains.
https://en.wikipedia.org/wiki/R%C3%A9seau_express_m%C3%A9tropolitain#Stations
A 4 car REM train with selective door technology could allow an extra car at each end to become a 6 car train. If there is enough level station clearance for significant extension, then the REM could easily run 6 or maybe even 8 car trains. Selective door technology is really good for trains limited to short platforms. It easily allows a 2 car extension of a shorter train. However, its still better that any half-length station has enough space for proper expansion.
Fortunately, the Edmonton_LRT underground stations were far enough away from the influence of the backwards BC planning mentality.
https://en.wikipedia.org/wiki/Capital_Line#Stations
| Churchill | Underground |  Metro Line Valley Line[a] | Downtown | April 22, 1978 | 53°32′39″N 113°29′21″W |
| Central | Underground | Metro Line | Downtown | April 22, 1978 | 53°32′28″N 113°29′31″W |
| Bay/Enterprise Square | Underground | Metro Line | Downtown | June 21, 1983 | 53°32′27″N 113°29′54″W |
| Corona | Underground | Metro Line | Downtown | June 21, 1983 | 53°32′27″N 113°30′21″W |
| Government Centre | Underground | Metro Line | Downtown | September 1989 | 53°32′10″N 113°30′37″W |
| University | Underground | Metro Line |
https://en.wikipedia.org/wiki/Metro_Line#Stations
Despite the Seattle Link_light_rail being much closer to backwards Vancouver than Edmonton is, Seattle had no problem with having longer underground stations than what's in shortsighted BC.
https://en.wikipedia.org/wiki/1_Line_(Sound_Transit)#Stations
https://en.wikipedia.org/wiki/2_Line_(Sound_Transit)#Stations
Fortunately, the Skyline_(Honolulu) like the REM can easily run 4 car trains, while the YVR-Canada Line is still just running 2 car joke trains.
https://en.wikipedia.org/wiki/Skyline_(Honolulu)#Route
https://en.wikipedia.org/wiki/Skyline_(Honolulu)#Rolling_stock
https://en.wikipedia.org/wiki/Skyline_(Honolulu)#Timeline_of_progress
The backwards BC mindset, or the BC Mind Virus hasn't been able to influence Alberta & Washington State, Hawaii & Australia...
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