I don't know about all the talk around this winter forum about knobbies for snow and CX for ice and low psi and such. My winter riding became easy when I switched to 23's no tread at 115psi. If you're riding the road you're only riding through ice -patches-, it's not as though the entire road is one big swath of ice in a city. You won't get traction on any ice that can't be cut by hard thin tires and you won't need any in those instances as the best way to ride over it is to hold your line and let your momentum carry you. The benefits of shedding, never having to clear ice from your ride, being able to get traction for acceleraton or braking from the asphalt or concrete beneath the snow or pack and not being at risk of a pinch flat far outweigh the "traction" looked for by riding on top of the stuff for me.