Gravel is worthless on snow/ice. Salt by itself is worthless on snow/ice. The answer to your road problems is a sand/salt mixture with most of it being sand. Minnesota uses a lot of salt in their road mixture and just look at their vehicles and you can tell where they're from without looking at their ugly license plates.
Their vehicles also rust out a lot faster than ours do in North Dakota. Also, having a fleet of snow removal equipment doesn't hurt the road situation either.
I've lived in North Dakota since 1981. I've been legally driving since I was 12. I have never used chains on my tires. Even driving through some of those passes in northern California where there are signs saying "Chains Required", I didn't use them. I was pulled over by CHP for not having chains and once they saw my ND drivers license, I was told to have a nice day and I was on my way with no ticket. Studded snow tires work when there is ample weight to allow the studs to dig into the ice. I've done a lot of ice fishing in my life and still haven't found a need for studded tires. I drive a 4WD truck and have been able to easily get around in the 23 inches of snow we've had so far this month. I'm hoping for a lot more. I love having my 8HP 24" snowblower. Bring the snow!!!