Chains help but for ice, studded tires are needed. I've used chains in deep deep snow, and they work, they're certainly a pain. If it's icy, they're certainly needed if you can't run studs. When snow gets packed by traffic, it's icy. Fresh snow, without anyone else on it is usually no problem for reasonably siped tires. Agressive mud and snow tires lack proper siping and are actually worse in snow than a well siped all terrain or purpose made tires like the Blizzaks (sp?)
__________________
|