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> ... because salt is mostly usable for light to moderate snowfall and ...

Perhaps more important - salt's effectiveness fades as the temperature decreases. Sand and gravel do not have that problem. So if you're running the Road Dept. in an area where serious cold ain't some rare event - why would you bother with salt?

EDIT: I know the "melt to pavement, solar heating finishes the job" tactic. Which can work with heavier snowfall, if you plow/shovel before salting. Colder weather inhibits both halves of the melt-&-heat. (Plus the further north you are, the shorter & slantier the sun's rays get, even on clear days.)

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DCH3416 6 days ago | parent [-]

Because the goal is to get the road surface exposed so it'll heat up and melt off the snow during the day. And then the residual salt will leave a residue which will help prevent refreezing.

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kube-system 6 days ago | parent [-]

That only works in places with relatively milder winter climates. In harsher climates, salt stops melting snow, and the surface temperature of even exposed road may stay below freezing even during the day.

	▲	DCH3416 6 days ago \| parent [-]
		Yeah. I'm familiar with the harsher climates aspect. The salt isn't really for the snow, it's for ice. Temperatures above like 10F, the sun will still cut through an untreated road surface and glaze over. Even with snow, because the top layer will still freeze, that nice crunch you get. The hazard is you have a smooth surface that your tires can't grip onto well when the sun goes down. I know it sounds counter intuitive but snow will still melt on very cold days because without wind you get a localized heating effect from the sun. The nice thing is, ice gets increasingly grippy the further down you go. It's the around freezing temps that get you. And bridges since rather than the ground holding temperatures, now you've got an air conditioning going on under the road. That's why salt is so useful over say grit because it changes the freezing point of the water.