Totally dependent on where you're riding and when. A lot of drivers won't be used to seeing someone out in the country in the winter. I ride in the winter but it's a fairly mild part of the country around here most of the time, especially the last few years. Salt is used around here on the roads and it will ruin derailleurs and chain pretty quickly. I wear a high-visibility construction parka and big sorel boots with wool slacks and splash pants if it's wet out. I've worn snowpants before but only in extreme cold. For me the biggest problem is sweating while riding and I usually ride with just ski goggles and no toque in an attempt to shed a bit of heat. I also wear a scarf on the inside of the coat that can be wrapped in a lot of different ways depending on the internal heat and precipitation. I usually carry a toque anyway and a spare pair of socks... usually I just have thin wool dress socks on but sometimes I'll double up if it's particularly cold. The wind in the open countryside will be taking a heavier toll on your body than you might be expecting as well.