Salt or Sand?

The winter season begins with a nice, big snowfall. Consequently, my car is covered with more salt than 100 supersize fries from mcdonald's. Which brings to mind the question: salt or sand? Some locales use only salt, some use only sand, and some use both. Salt, of course, works by combining with the water into an aqueous (saline) solution that has a slightly lower freezing point than garden variety H2O. The problem is that salt is corrosive and leads to lots oxidation (rust) on cars. Sand doesn't really melt the ice that much, but does provide traction. So I was just pondering what is a better idea for cities to use, salt or sand. Looking at my car, I'd give up a little traction for a little less corrosion. I have a feeling if you added up all the costs of using salt (such as corrosion) and compared it to the extra amounts of accidents from using sand, it would be better to use the sand. Oh well, just my ramblings, because I hate washing my car every fucking week!