I believe if we gave Toronto a long, hard look, we could conceive of some potential routes for cycling super-highways.
1) Finch Hydro Corridor - Basically is one already, just needs to be better connected with itself, and with adjacent parks and you got a east-west highway in the City's northern reaches
2) Martin Goodman Trail - If made wider and more direct at certain stretches, could double as one, although obviously lower speed than ideal, and a mixed-use trail once it reaches the Harbourfront area.
3) Beltline Corridor - Desperately needs to be connected across the Allen Road, and a more streamlined experience at a few other intersections. Afterwards, we would need some innovation on how to connect the Beltline to downtown Toronto, and then you got a corridor that connects the middle of the city with downtown.
4) Richmond Hill GO Corridor - If you have seen my lofty ideas in the Transit Fantasy Thread for abandoning the RH-GO corridor in favour of a DRL subway line that heads to Richmond Hill, then you might recall that I re-imagined the RH-GO corridor as a cycling superhighway extending south from the Finch Hydro Corridor all the way to where it would meet up with the Martin Goodman Trail. It might not be as direct of a route downtown as one would like, but it would be a route nonetheless, and a beautiful + picturesque one that connects to different parts of the city to boot.
What other potential routes could be imagined in the city?