If you are going to drive, you should clean off your car. You should clean ALL the snow off your car. Don't just clean off the windshield and rear window.
1. Clean the snow off the whole car.
Based on the type of snow that falls, you are either being a danger to yourself, or a danger to everyone else on the road (being a danger to yourself endangers everyone else).
There are pretty much two types of snow that fall, the dry snow (like central Illinois got last night) and wet snow (like we got last weekend). Dry snow is light, wet snow is heavy. Dry snow is the stuff that's bad for making snowmen and snowball fights. Wet snow is the kind you can pack, it rolls well, and balls well.
If your car is covered in dry snow, it will probably blow off as you are driving. If you didn't clean it off the hood of your car, then it will wind up on your windshield and you will have trouble seeing. If you didn't clean it off the roof of your car, it will blow off and cover your rear window, and wind up on the windshield of the car behind you.
If your car is covered in wet snow, it won't blow off as you are driving. This is the snow that you can knock off your car in one huge chunk. If your hood is sloped, you can just wipe off the front and the rest will come sliding down. If you don't clean off your car, the snow may not blow off your car. A much more dangerous situation can happen. I learned this the hard way, up in Alaska.
When your car has a thick layer of snow on the roof, it won't blow off. After you start driving, your car will heat up. The heat will normally cause a thin layer of the snow on that touches the roof the melt. As you are driving, it will be somewhat stable. If you stop suddenly, that thin layer of water, will cause the snow to go rushing forward. It will slide onto the windshield of your car. You will not be able to see. You had better hope that you don't need to see. Thankfully, the one time this happened to me, I was leaving a parking lot (after I had driven 20 miles with a foot of snow on the roof of the vehicle).
Look, that is a picture of a moron. Picture taken Wed, Feb 10 (while I was stopped at a red light). That is not overnight snow, that is snow that has been there a few days. The driver cleaned off the area above the wipers, and below the roof. It was either Texas or California plates. I would expect someone from either Texas or California wouldn't be familiar with driving in the snow. I would hope they would want to get their vehicle as clean as possible, since they were unfamiliar with winter-y driving. This person proves me wrong. If you see this person, beat them up. Please.
2. Scrape the entire windshield and all the windows.
Do not just scrape the driver side of the windshield. Do not just scrape a tiny section for you to see out of, you aren't driving a tank, you are driving a car. Any area that you don't clean will create a blindspot. There are people on the road who are dumber than you, you need to see them. You can't see them, if you don't clean off your windows. Do not attempt to clean off your windshield with washer fluid, use the scraper. If you use the fluid to melt the frost, do not drive immediately, wait until the entire windshield is clean. You probably won't be able to see out the back anyway, so you might as well scrape it.
If you are not scraping your windows and are using the defroster to clean it off, wait until the entire window is clean before driving. To hold the heat down better, put your visors down. Using the defrost will not get your side windows, so you'll have to clean them anyway.
3. Do not speed.
There is no point in going fast. The only place you'll get to quicker is your death. Slow down. Take corners slowly. If you are going fast and want to change lanes, leave plenty of space between you and other cars.
The slickest part of the road is the area with the white stripe. White reflects heat instead of absorbing. As you change lanes, if you hit the white paint, that is the area where your car is most likely to lose traction. Additionally, the lanes may be plowed, but the area between the lanes isn't necessarily plowed. The combination of snow and a colder area can lead to less traction. Less traction leads to the ditch.
4. Do not follow too close. Increase following distance.
You should be familiar with the 2 second rule. When the rear of the vehicle in front of you passes an object, there should be 2 seconds before the front of your car gets to that spot. When there's snow on the ground increase the number. If the car in front of you spins out, do you have enough distance between you to take action? If you are following too close, and they spin out, in 2 seconds you will hit the same area that they just went over, you are now probably spun out too.
5. Increase stopping distance.
You should start braking long before you get to the stop sign or other reason for stopping. Even anti-lock brakes can lock up if they aren't getting any traction. Just because you are sliding through the intersection, doesn't automatically give you the right of way.
6. Do not walk on the road.
Just because the sidewalk isn't shoveled doesn't mean you can walk on the road. You are not entitled to walk on a clean surface. It seems most people on the road now follow too closely, don't clean off their cars, don't increase stopping distance, and don't slow down; are these the people you are trusting to avoid you while you are walking on the road?
If you are at an intersection: even though you (as a pedestrian) have the right of way, do not walk in front of a car until it has come to a complete stop. It may take a second or two longer, but being in the cold for a second or two more, is much less time, than if you are being peeled off the hood of a car that couldn't stop.
Do not walk across the street (not at an intersection) if a car is coming. Even if on a nice day you would have plenty of time to make it. Do you have enough time to make it if you fell? Would that driver see you fall?
7. Remember the acronym COLD.
Keep Clean
Don't Overdress
Dress in Layers
Keep Dry
Clean clothes work better. If you are wearing polypropylene long underwear (fabric that wicks moisture away from the skin), it needs to be clean to work. If you are wearing Gore-Tex it also needs to be clean to work well.
Do not wear too many clothes. If you get too hot, you will sweat, if you suddenly get cool from sweating, that will freeze, and that is very dangerous.
Wear loose layers. Trapped air is what will keep you warm. If you have a big fluffy coat, ensure that it is big and fluffy, if all the air is out of it, it won't work. The most important layer you can wear is on your head. If you keep your head well insulated, you can probably get away with less layers elsewhere, temporarily.
Keep dry. Don't sweat, if you can help it. If you are sweating, dry off and remove a layer. If you aren't wearing layers, you can't remove anything (hence another importance of layers). If you get snow on you, brush it off. Don't take any snow with you to a place where it can melt. Brush it off your pants. Keep snow off your gloves. Wet gloves won't work.
8. Keep plenty of fuel in your car.
Don't run out of gas.
9. You aren't that important, just stay home.
Seriously, do you really have to go somewhere? Take the day off. Go play in the snow. Have a snowball fight. Build a fort. Clean the snow off your roof, then jump off it.
Have fun, be safe. If I see you without cleaning off your car, I'm going to yell at you and call you many many names, you won't be happy with me if I'm yelling at you for your stupidity.
