Plenty of responders here with more ice/snow riding experience than me but I've got to ask the OP what he considers "safe"? Do you mean "as safe as dry-road riding"?
I consider winter riding less safe primarily because motorists are more prone to lose control. I accept that increased risk, try to ride a bit more defensively, and ride anyway. Around here with the temp bouncing above/below freezing like a yoyo, patchy black ice is my nightmare and a guaranteed crash without studs.