Black Ice and the Law
We hope this isn't a surprise for you but if you cause a car accident while on black ice: you're still at fault. Weather isn't an excuse. Weather affects everyone equally. The difficulty or preparation that one person needs to make, everyone needs to make (including the decision to drive in the first place). Good judgment is a prerequisite for driving.
Because safer roads are a necessity for everyone during a snow storm or coldsnap, municipalities try to mitigate the affect of cold. They do this by spreading salt.
Salt: An Obvious Solution
Salt lowers the freezing temperature of water (meaning it has to get colder than 32 degrees before ice starts to form). No government in the US started salting roads until the middle of World War 2 when New Hampshire needed to clear a path to deliver materials necessary to the war effort. Northern states that experienced snowfall adopted the practice and currently 26 states spread salt each year.
Salt, unfortunately, is corrosive. It eats through the metallic structure of cars and the support frames of roads and bridges. Salt is making us safer in the short term, but endangering our infrastructure. This is the tradeoff we make every year.
The Future of Salt
Salt isn't going away anytime soon. Materials scientists are always trying to find less corrosive alternatives to salt (what have they tried? The leftover liquid from vodka distillation, beet juice, and pickle brine) but unfortunately most of these are cost prohibitive. So even some attractive solution like turning the road into a solar panel so that it could generate its own heat is several years away.
The most common sense solution to using less salt is to increase the reliability of meterological data and salt the roads before the temperature actually drops. Precision decreases the total amount of salt necessary to prevent black ice on the roads by about fifty percent.