I know that in the D.C./Baltimore area, salt is commonly applied both before and during snowstorms. When it snows, an armada of plows always seem to have the roads clear in less than 24 hours, and rarely allow so much as four inches to accumulate unplowed on significant arteries. But I have noticed in just the last 1-2 decades I have been conscious of it, that the quantity of salt used each winter seems to have increased a great deal (despite normal snowfall totals). It's no mystery that during said time period, average commute times have been increasing as people have chosen to live in evermore far-flung exurban developments. Concommitantly, the number of cars and miles of roads in service have also increased.
More recently, I noticed that in the Portland, OR area, a mixture of gravel and sand was more popular. And many drivers apply chains to their wheels despite the extra wear and tear this puts on roads. Knowing that high salinity is potentially problematic to the water table and local agriculture, I suspect this is part of the reason why Portland chooses to rely on a more traction based method as opposed to a chemical melt method. Salt also tends to rust-out cars, but as fiberglass bodies have become more common in recent decades, this probably isn't as big a problem as it used to be. It may even be a cause for the increased salt use I perceive.
So I wonder, what do people know about the trends for salt use in snow removal in the U.S., Canada and other snowy parts of the planet? Does it seem like it's been increasing over the past few decades? What is known about the consequences of salt use? What is known about the consequences of gravel and sand use? Or how about the damage done to roads by chains on tires? Are different methods more popular in part based on whether temperatures are very extreme, and or if snow totals are very heavy? Obviously, salt alone won't take care of 3 feet/1 meter of snow.
I'm curious as to how the answers to these questions differ regionally, as well as the answers themselves. So please include locational info for the areas for which you describe snow removal methods, trends and their effects. Also, how do you explain any trends that you see are occuring? Thanks.