Regarding our earlier discussion of the boarding efficiency of different platform heights, I decided to do a comparison of rolling stock.
For 610mm double-decker coaches, I used our current BiLevels. I excluded the locomotive because it doesn't need to fit on the platform.
For 610mm single-level EMUs, I used the Stadler FLIRT, which is currently the only FRA-compliant single-level multiple unit with 610mm. I combined the floor height of TexRail's FLIRT DMUs with the other stats of NS's FLIRT EMUs.
For 1220mm single-level EMUs it's technically possible to have more than 2 doors per side, but I couldn't actually find any FRA-certified examples. So I used a hypothetical version of the Kawasaki M8 with 3 doors per side.
View attachment 385318
So it looks like even with GO's 610mm standard, single-level EMUs could have 25% more doors per side than GO's current trains. And considering that single-level trains would have fewer total passengers than BiLevel trains, the time to load and unload passengers at stops should be considerably lower.
It looks like low-floor single-level EMUs could nicely complement BiLevel coaches, with the EMUs operating local services on the central segments (e.g. to Bramalea, Aurora), while express services continuing further out are operated by BiLevel coaches hauled by diesel/bi-mode locomotives (e.g. to Kitchener) or electric locomotives (e.g. to Barrie).