Na's Safest Vs. Most Unsafe Roads

In September I'll be going out to Yellowstone Park so I got thinking:

Ontario and Massachusetts have the safest roads in North America (lowest fatality rate).

Wyoming and Montana have the most unsafe roads in North America (highest fatality rate).

Any thoughts on why that might be? Curious as to what you think.

(Side note: I've found drivers in Montana and Wyoming to be much more courteous than their counterparts here in Ontario and in Massachusetts... so... why such a big difference?)

Do those states use salt in the winter? Could be a combination of being able to keep older cars along with bad winter conditions (I think some areas of Montana get pretty big snowfalls). Road design obviously plays a factor, but I'm not familiar with any of those states so can't comment.

The roads that remain open during the winter get some salting. Some of the roads through the mountain passes in Montana and Wyoming are closed during the winter, due to lack of winter maintenance, and some of them are avalanche hazards.

Ironically, the National Motorists Association (not to be confused with AAA or CAA), listed Wyoming as the "friendliest" to drivers, but it consistently ranks in the top three in terms of fatality rates. Conversely, Massachusetts, which had the lowest fatality rate, was the 2nd most hostile, according to the National Motorists Association. Go figure that one.

I guess you can't be too friendly or else really poor drivers will manage to function on the roads until they really screw up.