Yeah, studded tires.

If you live in a place that just temporarily has ice sometimes (not Minnesota, where I live), you can get by with a cheaper pair of Nokia A10's.

My favorite is the Schwalbe Marathon winters, though, myself. At high psi the outer row of studs doesn't come in contact with the ground, so they roll faster.

All options are a little slower than no studs, though. The Marathon Winters have been the best studded ones.