Rock salt is the most economical and readily availible product. But its corrosive, not only to our cars, but also plant life and infrastructure as well. Many steel and concrete bridges suffer from corrosion related damage more than anything else. This is exacerbated by municipalities that spread salt for every storm, including a pre-treatment so that people that "need" to be on the road can be safe. Here in MA, we have this ridiculous budget issue where, if they don't use all or more of their allocated amount, they recieve less money the next year. Salt, being fairly expendable is then spread generously for even the slightest threat of adverse conditions under the guise of "safety".
Less corrosive alteratives are availble, but more expensive. Magic Salt is a regular rock salt treated with some kind of liquid byproduct from brewing beer. It supposedly increases the effectiveness and reduces the corrosivity.
