David in Denver, Im living in Northern Sweden and I take my son to day care everyday by bike. During the summer months I used a child seat on the bike and had smooth (ish) tyres on my bike. I have changed over to use a child trailer or whatever you want to call it as I thought the bike seat may be too dangerous in the snow and ice. I have also changed the tyres to studded tyres for the first time. They make so much difference although one piece of advice is to ride them with a little less pressure in them so you dont get the feeling of riding on ball bearings. Another thing to note about winter tyres is that they are said to be made of a type of rubber that doesnt get hard when they freeze, this helps with the grip on the ice. This could be a problem with knobbly regular mountain bike tyres. You can also use studded tyres on the roads without ice or snow for traction, but do keep the pressure down as I said...