One, on many routes, the traffic is the personal vehicle, as opposed to the service vehicle/truck..
If one can remove 10-50% of the passenger cars by providing higher quality transit, it ought to be plausible to reduce some roads without car-capacity replacement.
I'd also put in for cutting the maximum size of trucks on City streets; I remain of the view that the 53-footers were always a mistake, as City road geometry does not and cannot support them at most intersections.
Going back to '48 Max would be prudent.
None of the above, unto itself creates greater safety for cyclists or pedestrians.
Narrowing roads can be helpful; cycle tracks with physical separation even moreso.
Truck size definitely has to be addressed. I would be concerned about width as well as length.
Two lanes for truck routes instead of four might actually be safer, from the perspective that even with a marked bike lane, it is virtually impossible for a vehicle to drive alongside a large truck and stay safely away from both the truck on one side and cyclists on the other. No amount of paint or soft barriers will correct that. But, if there are too many vehicles, and we downsize them.....
I don't have any data on Dufferin either, although my impression from my own driving is it's one of the more major routes for trucks. And somehow it's a road that encourages impatience.
I wouldn't discount the idea of taking parallel side streets, declare them auto-free, and connecting them. In this case, Gladstone runs mostly parallel to Dufferin. Fill in the gaps, give it stop lights at major cross streets (with priority equal to what motor traffic is afforded), realign the stop signs so that they favour through bicycle movement... in effect it becomes an "arterial" for cyclists but vehicle free. That achieves a physical separation that just may be too hard to make work on some main arterials.
But some portions of these issues are about driver education; distractions while driving, visibility (here I'm not on about clothing or such, but about the way in which streetlights are often more harm than good)....
Driving has a high potential for sensory overload. It's probably the highest-CPU-load task the average person attempts. Inattention exacerbates this risk, certainly, as does speed.... but even cautious, attentive drivers are challenged to process everything. Reducing clutter, simplifying signage, and addressing sight lines and day/night visibility all are needed.