I'm very aware that my comment was very much from a non civil engineer point of view, and as you bring up, there's lots of factors involved here. Will be a real challenge finding solutions and or the best big picture and long term budget solutions.
Thanks for the added details.
There is always a solution if you spend enough money.
It reminded me to check on the Kicking Horse Canyon project on the trans Canada highway, east of Golden B.C.
This has been going on for years, and the last 4.8 km phase was announced in late 2015, and they still haven't started construction although it is scheduled for this spring.
$600 million for the last stretch, estimated completion 2024. With any luck the pandemic will have abated by then. They do mention room for bicycles, that should make the Golden Triangle ride much safer.
Realign 13 curves and widen the highway to four lanes with median barrier and wider shoulders to accommodate cyclists
https://www.kickinghorsecanyon.ca/ab...ject-overview/