As Dave mentioned, those are perfectly good roads, but they are mostly 2 lane roads, and more importantly, they go through some pretty remote, unpopulated areas.

If the roads are clear, it's a great and very scenic drive, but if there is a chance of bad weather, I would look for other routes. It will likely take a far bit of time for such roads to be cleared and treated, and you'll have long distances between places to stop to wait out a storm if needed.