Winter driving

Anyone who's going to drive at high latitudes or over mountain passes should consider the possibility of snow, ice, or freezing temperatures. On icy and snowy roadways, friction is low and you cannot drive as if you were on bare asphalt. Sliding off the road and collisions are much more likely than in good conditions.

“

Drivers ignoring winter conditions may be subject to natural selection

”

—Highway sign in an Internet meme

On the other hand, icy and snowy conditions are normal in many countries, and traffic goes on mostly uninterrupted all year round.

During blizzards, enough snow to get you stuck can fall in very little time. Visibility may also be restricted by falling or blowing snow or by condensation or ice on vehicle windows.

Cold weather is hard work for the car. A weak battery, ice on electrical parts or in fuel, frozen diesel, or a frozen cooling system may cause your car to break down. If you get stuck, you may be at risk for frostbite or hypothermia; see cold weather, snow safety and ice safety for discussion.

Understand

Winter driving conditions

If you have never driven in freezing conditions before, it's easy to underestimate the variety of driving challenges that winter weather can throw at you. Consider taking an advanced drivers education course, especially if you have no or little experience driving on snow or never learned how to recover from a skid or similar conditions.

Heavy snowfall — Heavily falling snow can greatly reduce visibility, in some cases down to just one or two meters (a few feet). Also, road maintenance equipment may not be able to remove the snow quickly enough, which may cause motorists to become stuck in snow and stranded. This can happen even on good, heavily-travelled roads with a high priority for snow removal.

Blowing snow — Wind can blow snow across a road that was bare, making those sections more slippery. Blowing snow can also reduce visibility and tall snowdrifts may suddenly block the road ahead.
Blizzard — A blizzard is falling snow together with a strong wind, which may greatly reduce visibility and cause snow to blow across the road.
Flash freeze (cold snap) — In fall and spring, roadways can be wet with rain or melting snow. If the temperature suddenly drops below freezing, the meltwater turns into a very treacherous coating of ice.
Freezing drizzle or freezing rain — Rain or light showers that quickly freeze when hitting the ground or other surfaces, coating roadways with ice. When the rain is supercooled (below freezing) the surface does not even have to be cold. In some situations, freezing drizzle can freeze to windshields, and the only way to clear it is to repeatedly spray the windshield with washer fluid containing antifreeze.
Black ice — Ice that freezes in a transparent layer over a roadway, creating the illusion that the road is ice-free. Black ice is most often found on bridge decks, ramps, and overpasses, but can also occur on other road sections. Frequently encountered just before and after sunrise, before the road surface warms.
Low light levels in daytime — Heavy winter cloud cover can sometimes make daytime driving more like driving at dusk. Be alert to low light conditions, and turn on your headlights so that your taillights will go on, and increase your visibility to drivers behind you. Some countries (Canada, Nordic countries, Russia, Iceland, Baltic states, most of Eastern Europe, Switzerland, Italy) require vehicles to be equipped with daytime running lights for greater visibility; these usually activate headlamps (or at least the fog lights) whenever the vehicle is in motion but do not activate tail lights or other markers. At high latitudes in winter, the sun is also low on the horizon for a long period of time. Visibility can be very poor due to glare, so wear sunglasses.
Few hours of daylight — In high latitudes there are few hours of daylight in midwinter. In places such as northern Scandinavia, the sun may not rise at all, with only an hour or two of dusk in midday. In practice, you must drive in darkness or dusk.

Be extremely cautious on bridges and overpasses. Because they do not have earth under them, they may be colder than other parts of the road and may have ice when other areas do not. Also, sliding off one of these is often worse than just sliding into a ditch.

Risks of winter driving

Collisions / skidding. Roads slippery with snow or ice can cause vehicles to go out of control easily. As always, cautious and experienced drivers can be the victims of careless drivers. Braking distance increases dramatically on ice or snow. Handling is seriously impaired on ice, slush and snow. Animal collisions are more probable at winter, as animals tend to approach valleys and human settlements in search for food – or just use the road to avoid deep snow.
All too common,
especially with summer tires
Stuck vehicles. Slippery roads make it easy to slide right off the road into a ditch or a snowbank. A minor collision can also push your car off the road. If you end up in deep snow, it can be very difficult to get your car back on the road, especially if you don't have the right equipment in your car for such a situation (e.g. shovel, traction mats).
Stalled vehicle / vehicle won't start. Cold weather is hard on cars, especially car batteries. An interior light left on while your car is parked for several hours may mean that your car won't start when you return. If you are lucky, a tow truck, taxi or a fellow motorist may be able to jump start (boost) your car using jumper cables. Automobile association members (or anybody) may obtain roadside assistance from the club. Some cars (with manual gearbox) can also be started by pushing and engaging the transmission at speed – but this will break the gearbox on other cars. Engine oil in diesel engines may thicken when too cold, preventing the car from starting or stopping the engine even when already running. Drivers in cold areas often have mains-powered engine heaters fitted, to warm up the engine before the start.
Stranded in your vehicle. Sudden severe weather conditions can lead to you being stranded in your vehicle for several hours or overnight, even on a busy, well-maintained roadway. If your vehicle gets stuck on a quiet road, you may be stranded much longer.
Hypothermia. If you end up stranded in your vehicle in cold weather, hypothermia is possible. You need adequate warm clothing and/or blankets.

Prepare

Choosing the right vehicle

If you have more than one car to choose from, then think about the points below. If your own car is not equipped for winter conditions, it may be cheaper and easier to rent a car at the destination. Then you are able to choose and hopefully get one suitable and already equipped for the local conditions.

A four-wheel-drive (4WD, 4x4) vehicle is better able to climb slippery hills than a two wheel drive, and four wheel drive is very useful getting out of snow drifts. However, they do not allow higher speed around corners and braking distance is the same. In fact, they are much more prone to accidents on snowy or icy roads, probably as they give less early warnings. Two-wheel-drive cars are fully adequate on most maintained roads.
Front-wheel-drive (FWD) is generally preferable to rear-wheel-drive; traction may be better and skids during cornering are easier to control. Nearly all post-1990 small and medium-sized cars are front-wheel-drive – if you are unsure, check the owner's manual.
Anti-lock (ABS) brakes prevent wheels from locking on slippery roads, thus allowing the driver to steer the vehicle while braking. This comes at a price – increased stopping distances and higher costs for brake repair and maintenance due to the added complexity of the system. All cars made since 2004 in Europe and Japan must have ABS, as do all cars in the USA since 2012.
A vehicle with a limited-slip differential or traction control is recommended for driving on snow and ice. The differential (diff for short) distributes power evenly to both left and right wheels while allowing each wheel to turn at different rates (slip) while cornering. If one wheel is on ice or buried in snow, that wheel will spin freely wheel with very little power, while the opposite wheel will receive insufficient power to move the vehicle. With a limited-slip differential, the diff will lock the two wheels together if the slip between the two is excessive, transferring power to the non-slipping wheel.
Conversely, if you do find yourself stuck, shutting off traction control may actually help you rock the vehicle free.
A small, lightweight 4x4 vehicle with good ground clearance is preferable to a SUV or off-roader, especially on mountain roads. Narrow tires perform better on snow than wide tires. Heavy vehicles are more likely to slip on steep roads, and are also more difficult to rescue by pushing. Also, if your car has a low road clearance, that bucket-sized piece of ice you might encounter on the highway will in the worst case damage the oil pan, exhaust pipe or something else under your car.
The same rule applies to two-wheel-drive vehicles: A small car is better for snowy conditions than a mid-size or luxury car.
Be aware that "all wheel drive" is not four-wheel drive. AWD is a computerized system that attempts to compensate for road conditions as they occur. While this can be helpful in some conditions for persons with limited winter driving experience, it is not a substitute for knowing how to handle your vehicle and should not be taken as equivalent to 4WD.
Pickup trucks, vans, and SUVs all have a greater tendency to slide on slippery roads, particularly on turns. People who routinely drive these vehicles in winter conditions often put weight (sand bags) in the vehicle near the rear axle to reduce this behaviour.
Pickups with "dualies" (four wheels on the rear axle) handle extremely poorly in winter conditions and are not recommended.
100% electric cars might not be suitable for long-distance winter driving as battery charge is greatly diminished in cold weather. Some experience with electric cars and charging is useful. Planning should account for busy or unavailable charging stations, and take into account the reduced range and longer charging times in winter conditions.

In electric cars, cabin heating uses battery power, decreasing range even more (while cabins of combustion engine vehicles are heated using waste engine heat). If the battery of an electric car loses its charge, towing might be the only option. Some electric cars save battery power by using heat pumps (reversible air conditioners, which heat as well as cool), but these degrade in performance in below-freezing temperatures and typically stop working completely at −15 to −25°C. Hybrids (e.g. Toyota Prius) will overcome these problems by using their combustion engine more, so for them the cold just affects the fuel economy.

In Europe, you can buy cars with self powering (using the fuel of the vehicle) block heaters. These will preheat the car at a predetermined time or via remote control. Although this can add considerably to the purchase price, there is payback over the vehicle's life, with somewhat reduced fuel consumption and less engine wear at start-up, in addition to the added comfort.
Seat heaters are standard in cars produced for the Nordic market. They are very nice to have when entering an otherwise cold car. After-market heated seat pads, which plug into the car's power port, are also available. Note, however, that adding many electricity consumers strains the car's generator and battery.
If possible, don't rent a white-colour vehicle if you're planning to drive outside of populated areas. It makes you harder to spot in snowfall, and for rescuers should you become stranded. However, this is a minor issue compared to finding a vehicle equipped for winter conditions.

For extreme conditions, such as expeditions to remote uninhabited areas, the vehicle should be equipped with a winch to pull itself out when stuck. It is also usually advisable to travel in a convoy with several vehicles; this greatly improves your chance of survival if one car breaks down or crashes.

Preparing your vehicle

Have a good mechanic check over your vehicle with a view to winter, or do it yourself. Among the things it may need:

Winter tires, or at least "all weather (all season)" tires depending on how much winter you expect to drive in; see Tires below.
Antifreeze in the cooling system (ice can destroy the engine). Check the levels and change out if the coolant is old (two to four years, depending on type used). The typical 50/50 mix of radiator antifreeze has a freezing point of about −34 °F (−37°C), which may be insufficient in some areas, such as northern parts of Alaska, Canada and Scandinavia, where temperatures can drop below that in a typical winter. A solution of 70% antifreeze and 30% water can prevent freezing down to −84°F (−64°C).
Replace worn wiper blades. Wipers designed specifically for winter are heavier than the standard blades.
Non-freezing windshield washer fluid. Don't use plain water for your washer fluid as it will freeze. Do not use antifreeze intended for the radiator either, as it may damage your vehicle's paint. Look for the winter-type washer fluid at auto parts stores. Winter washer fluid is also readily available from gas stations in winter weather destinations. It has a freezing point of about −20F/−30°C. Even though it's on the other side of the windshield, using the defroster also helps prevent the washer fluid from freezing. It's good to have an extra bottle of windshield washer fluid, particularly when travelling on salted roads or in spring when the snow is melting.
Lower-weight thinner engine oil, since a higher summer weight oil may become thick enough at low temperatures to prevent starting.
A checkup for the battery, charging and starting systems; batteries perform poorly at low temperatures, and a cold engine is harder to start. Have the battery replaced if it's near or over the pro-rated warranty period. On an older vehicle, check the belts, and an alternator test is also a good idea. Fill an older, unsealed battery with distilled water (but don't overfill).
A checkup for the exhaust system; in a stuck car, you may need to run the engine to keep warm, and an exhaust leak could be fatal.
Check the heater and defroster, and make sure they heat with no smell.
An engine block heater is recommended at least if you are expecting the weather to reach below −25°F (−30°C).
Automotive rustproofing protects the vehicle from corrosion, a common issue in areas where salt or sand is applied heavily to icy winter roads.
Make sure brakes and ABS system are in good condition.
On older vehicles, consider replacing the dome light with a compatible LED. LEDs use much less power, and it takes a lot longer to drain the battery if it's accidentally left on or needed for rescue.
If your car has traditional locks that are opened by regular keys (including the fuel tank cap), you should have a bottle or can of lock antifreeze fluid at hand. In some cases some water might have gotten into the lock and frozen, preventing normal operation. Keys old enough not to have electronics in them can also be heated with a cigarette lighter and put into the lock, but you shouldn't attempt this with modern keys. Use body heat or some suitable key substitute instead. If trying to force the key into or around a lock that has frozen in place, you may in the worst case end up with one half of the key in your hand and the rest in the lock.
For outdoor parking when it's snowing or cold enough for ice to stick to the car's windows, a tarpaulin can be useful to reduce the time and effort needed to remove snow and ice when it's time to get going again. Big tarpaulins can be used to cover the whole car, and then there are smaller ones that only cover the windshield and are fastened by magnets.

Tires

In many northern countries, and mountainous countries elsewhere, such as Armenia and some Balkan countries, winter tires are mandatory in winter and possibly in winter conditions outside the set dates. The definition of "winter tires" varies; enough tread depth may suffice legally, but you will want to have enough traction. Proper winter tires are often studded, but they don't need to be. "All-weather" tires may be enough, but unstudded "Nordic" winter tires are much better when it is cold.

If renting a vehicle, in some countries you must specifically ask for winter tires.

Check the condition of the tires and their pressure. Don't forget the spare tire and jack.
Check that the tires are proper winter tires, and not just "all-weather" or "mud & snow" (M&S) tires. Although these satisfy the legal requirements in some countries, they leave much to be desired in cold conditions. In some areas you could get away with normal tires, using cables or chains as needed.
Studded winter tires are good for most winter driving conditions, particularly on icy roads around 0°C. However, it is important for you to know the local regulations, as some places prohibit them, year round or except winter or wintry conditions. The regulations can be on country, state, province or city level, or even for some part of city centres.
Unstudded "Nordic" winter tires are good in general winter conditions such as slush or hard snow, but not as good as studded ones on smooth ice. They are legal any time, but less good in warm weather, just as all-weather tires are not good when it is cold.
Without winter tires, you should always bring tire chains or cable chains, but note that chains are not useful for long distances (use over a mountain pass, but no further). Winter tires are enough in most conditions. Sometimes chains are needed (legally or otherwise) even if you have winter tires.
For AWD/4WD vehicles, all four tires should be of the same size and tread pattern (i.e. usually the same model number of tire) with a similar thread depth. This applies to both all-weather and studded tires. The more recent and "computerized" the AWD/4WD vehicle is, the more this holds true. Failure to do so may result in costly damage to the differential, and leave you stranded in the cold. In some vehicles, a smaller-sized spare tire may be temporarily used for a limited number of miles at moderate speed. Unfortunately, if just one tire is damaged and the overall tread wear is below about 70% remaining, all four tires will need to be replaced. Even if it's above 70%, the tire may have been discontinued and unavailable. Getting a fifth new tire as a full-sized spare (and including it with the others in routine tire rotation) is a good idea.

Tire and cable chains

In the most difficult winter conditions winter tires may not be enough. Especially in mountains and on less maintained roads, chains or cables should be considered. Note however that for instance in Finland, Norway, Sweden, and Canada, on public roads good quality winter tires are generally sufficient for light vehicles. Chains are not an alternative to good quality winter tires for longer distances, nor should they be used when driving at highway speed. Rental car companies may not permit you to put chains on their vehicles, because improperly attached chains may damage the vehicle's paint or dent the body.

Tire chains give better traction than cables, but are more difficult to install and remove. Cleated chains provide maximum traction but are very rough to drive on. Know your tire size (e.g. P195/60R-15) before purchasing. When needed, install on the drive wheels (i.e. front for front-wheel-drive, rear for rear-wheel-drive). For 4WD/AWD the front is usually best, but check the owner's manual. Only use chains or cables in snow or icy conditions, and remove them as soon as they're no longer needed. Don't even try them on for size on a hard, bare surface such as concrete. They might spin out and damage the chains, concrete, and/or wheel well of the vehicle, and possibly injure someone.

Fuel

If your car has a diesel engine, make sure you've filled up with the appropriate variant of diesel. In countries with freezing temperatures during the winter, winter diesel, sometimes known as alpine diesel (diesel with additives to prevent it from gelling) is sold at gas stations during the winter months. However if you don't drive often, have filled up in a warmer country or area, or the temperature has unexpectedly dropped to freezing overnight, you might find that the "summer" diesel in your fuel tank has turned into a tacky gel which will clog the fuel lines and starve the engine. Also, if you have a spare can of "summer diesel", you should not use it in cold weather. In areas like Finnish Lapland where the weather gets really cold (under −30°C), arctic diesel with an even lower cold filter plugging point is usually available.
There might be small amounts of water in your fuel, which freezes to small ice crystals that can block your fuel lines. There are additives (gas-line antifreeze) available that can prevent this. It also helps to keep your gas tank at least half-full at all times, to reduce condensation.

Bring

Satellite navigation units (GPS; Garmin, Magellan, TomTom, etc.) for road travel have become so inexpensive that anyone doing winter driving beyond their home area should use one. Be sure it contains maps of all relevant countries if you cross international borders, and don't wait until the last minute to figure out how your unit works. Ideally, you should have at least a month of experience in your home area before going on a long winter road trip. Practice using your GPS even for driving to familiar, nearby locations. Be certain any hand-held unit is suitable for navigation while driving, with spoken turn-by-turn prompts, and get a mount for it. Be aware that the device may act strangely in special situations (such as a road ending at a ferry quay) and may loose satellite contact in heavy snowfall. A GPS device intended for just hiking, boating, and the like is not suitable while driving.

In addition to the above, these things can be helpful for any winter trip, even a short drive in the city:

Warm winter clothing, including ski caps, mittens, scarves, etc. appropriate for the conditions outside, even if you are going on a short drive from one heated parking garage to another. A minor collision could change your plans. If you live in a mild climate and can't find winter clothing where you normally shop, try a sporting goods store or outdoor sports shop. Shops for farmers' and lumberjacks' equipment often offer solid winter clothes at a modest price.
Leather driving gloves, or warm winter gloves with leather palms for gripping the steering wheel. The steering wheel can take a long time to warm up once you start the car.
Sunglasses. Although winter weather is often cloudy and dull, on a sunny winter day, the glare on the road from snow (or even water) can be quite bad. The midday sun is much lower in the sky at high latitudes and slower to rise and set than at the lower latitudes. This means it's more likely to get in your eyes while driving, especially in the morning and evening. Sunrise and sunset may be the only times in the day that the sun drops below the cloud layer.
Ice scraper with a brush (the latter especially for cold powder snow). De-icing spray. Extra scraper.
Jumper (booster) cables. At extremely cold temperatures (under −30°C) it can be a good idea to have a charged spare battery that you keep indoors overnight.
Starting fluid, a spray that can be bought at gas stations and car spare part stores in countries that experience cold winters. This diethyl ether based stuff has a low ignition point which means a lesser burden for the car battery (which holds less charge at cold temperatures) when starting the engine. In cold weather, spray some in the air intake and try starting the car immediately afterwards while pressing the gas pedal slightly. To avoid engine damage, don't use too much of it; just spray for a second or two before each start attempt.
Road maps.
Emergency road flares or a warning light, to mark the location of your vehicle at night in case of breakdown.
Cell phone and its in-vehicle charger.

If you bring any medicines, don't leave them in a parked car, where they could deteriorate by freezing. Have them somewhere easy to reach for situations where your car may get cold without your taking out your luggage (intermediate stop, breakdown).

It's a good idea to always have a spare 12V charger (via the round power outlet) in your vehicle. Nowadays the standard solution is to use the outlet for an adapter with USB outlets, and a charger cable for your phone with a standard USB connector (normally connected to the transformer part for 110–230 V AC – some chargers have the cable fixed to the transformer, in that case get another one; for old phones you may have to buy a dedicated model-specific in-vehicle charger).

Cellphone service may not be available in rural areas; in truly remote locations (like the Trans-Labrador Highway) only a satellite phone may receive signal. If you're planning to upgrade or replace your cell phone, look for a model that includes GPS (most do). The GPS in a simple flip-phone can report your position to emergency services to locate you, but are otherwise not useful for navigation. Smartphones may be able to download apps with OpenStreepMap-like data and use GPS for navigation. Keeping a spare cell phone in the car (off, charged; preferably also its in-vehicle charger) is always a good idea no matter the weather. In the U.S. and EU, 9-1-1 and 112 calls (respectively) will still be connected even if the account is inactive and has no funds, in most countries even without a SIM card. CB or ham radio may be useful if other users of the same roads are monitoring and if your vehicle's battery is OK; users on some remote logging roads still monitor CB 19 (especially in USA and Canada, but also some other countries) as mobile telephones have very limited range from the base station.

Winter emergency kit

For trips outside of cities, put together a winter emergency kit. It will help you stay safe or even recover from many winter road emergencies, including being stranded in your car for several hours or overnight. Here are some of the things that you should consider putting in your emergency winter kit:

Extra non-perishable ready-to-eat food. Always have high energy snacks, such as chocolate or cereal bars, and drinking water in the car.
First aid kit. Consider including a "space blanket" (heat-reflecting thin cloth to wrap around a person).
If you take medications which are essential or cannot be interrupted, make sure you take extra medication with you.
Blankets or sleeping bags. If possible, keep them in the passenger compartment, not in the trunk, so they won't be freezing cold.
Lighter and matches, or similar.
Candle placed inside a deep tin can: if possible, use the candle for heat rather than the car heater, should you get stuck. Open a window slightly on the side of the car sheltered from the wind to let in fresh air.
Portable radio with AM band and batteries, or a wind-up radio, in case your car battery goes flat.
Flashlight (torch) with batteries, or a wind-up flashlight. Batteries should be reversed so that they won't be drained if the flashlight is accidentally switched on.
Spare batteries for radio and flashlight, if they use batteries. Warming the batteries in your pocket or hand before use will extend their capacity.
A lightweight snow shovel (or any shovel, if you can't buy a snow shovel locally).
Bucket or bag of sand or similar to get traction in case your vehicle gets stuck, especially without all-wheel drive. Sand is useful also to add weight (and thus traction) on driving rear wheels. Other options include non-clumping cat litter and commercial traction mats (or a strip of carpet) to be slipped under the driving wheels.
Tire chains or cables (see separate section, above).
Fluorescent banner to make your vehicle easier to spot in the daytime. Reflecting vests are also good to have in case you must stand or walk on a trafficked road – in many European countries, it's actually mandatory to have one in your car.
10 metres of light (parachute) cord or rope, to use as a homing line (see below).
Things to keep your spirits up, preferably without need of electricity. You could write a list of games you'd enjoy and that don't have physical requirements and keep that handy. Story telling? A deck of cards and a portable chess board could also come handy. Snacks and drinks can play a role, but use those sparingly, at the pace you'd need them. An Arctic night can be quite long, and you won't be rescued at first dawn.

For really difficult winter driving – off-road or in isolated areas – you may need more serious equipment. In some areas the minimum safe vehicle has four-wheel drive, a winch, and a roll cage. You also need a two-way communication system – radio or satellite phone – to call for help if needed and equipment like a good tent and propane heater to survive until help arrives.

Go

	Note: It is always best to avoid driving when road conditions are poor or the forecast is bad.

Weather and road conditions

Check the weather forecast for all areas you're planning to drive through, in order to avoid driving in severe winter weather conditions (heavy snowfall, blizzard). Winter weather can turn bad very quickly. If at all possible, allow for a couple days of flexibility so you can wait out a winter storm (preferably before leaving home). If you know the forecast before departing, you can try to avoid the worst of it. Weather can be much colder or harsher in areas that you are passing through than it is at your departure point or destination, particularly if you are driving from coastal to inland areas, or from lowlands to highlands.
Check the road conditions for the roads you're planning to use. Many places have online road reports, news reports may include coverage of road conditions in the area, or there may be a phone number (such as 5-1-1 in much of North America) that you can call for a road report. In the USA, include the word "state" (i.e. "Montana state") in your search; the term "road report" or "road conditions" may also be helpful. Road reports can tell you if roads are closed due to heavy snow, blizzard, or avalanche control; if road conditions are so poor that driving is not recommended; or if there is convoy driving only. Road authorities also operate online webcams that offer real-time images of road surface at select points along each route. Note particularly the conditions in mountainous or steep parts of your route.
Always get advice from locals beforehand about conditions off the main highways. The best route may not be obvious to you, or even be shown on a paper map.

Itinerary

Be aware of early sunset times in high latitudes. Some examples from the northern hemisphere at the winter solstice on 21 December: Anchorage, Alaska 3:41PM; Fairbanks, Alaska 2:40PM; Banff, Alberta 4:37PM; Boston, Massachusetts 4:15PM; Chicago, Illinois 4:23PM; Irkutsk, Russia 4:52PM; Yakutsk, Russia 2:53PM; Stockholm, Sweden 2:48PM; Nordkapp, Norway no sunrise at all, twilight ends 12:49PM. And for the southern hemisphere, where the winter solstice is on 21 June: Christchurch, South Island 4:59PM; Hobart, Tasmania 4:42PM; Invercargill, South Island 5:06PM; Punta Arenas, Chile 5:31PM.

If using a GPS device, mapping software, or websites to plan your route, always double-check with a reliable detailed map, such as printed maps of Rand McNally, AAA/CAA or Michelin. Always select the "fastest" (never "shortest") route, as this will help keep it to the main highways. Of course, you shouldn't drive faster than conditions permit. Selecting "shortest route" or otherwise taking short cuts in wintertime could easily get you stranded, and can be deadly in remote enough areas. Keep in mind that the GPS may suggest temporarily closed roads, or roads that are difficult to drive in winter conditions. Real-time updates have become quite common, but this varies by model and area; get last minute information from local road authorities.
Avoid anything below a state/provincial route except for the last few miles/kilometres to your destination, where necessary. On some minor roads, there might not be another vehicle for days, weeks, or even months. Software maps are not as good as paper maps in showing how "minor" a less-used road is. Some aren't even paved, but look as good on a computer screen or GPS device as a well-paved, busy thoroughfare. That said, some government maps may have all state/provincial routes printed with equally bold lines, regardless of how well maintained and frequently travelled they are. Commercially produced maps are often much better at distinguishing major highways from minor ones.

Other

Leave a travel plan with a friend or family member if you are planning a long drive, driving in an unfamiliar area, or know that the weather or road conditions will be a challenge for you. Your travel plan should include the route that you plan to take, where you are going, and when you will check in with the person holding your travel plan. Tell them a hard deadline when the person holding the travel plan must alert authorities if you haven't checked in (but allow for unplanned stops somewhere without mobile phone coverage). The travel plan will let them know where to search. A travel plan may feel like it limits your spontaneity, but with modern communications, it is easy to let people know about a change of plans even if you make it at short notice. If you are somewhere without communications, better safe than sorry.
A particularly difficult combination is blizzard conditions (where visibility is reduced by blowing snow) combined with early sunset (so headlights are on and being reflected back into the driver's eyes). This accompanies dangerously snow-covered roads (with reduced traction and inability to see any painted lane markings on snow-covered asphalt). While the first obvious advice is to slow down for conditions, on busy highways operators of large trucks often refuse to decelerate, instead repeatedly passing other vehicles. This dumps more snow and slush onto windscreens, making an already-bad visibility problem worse for drivers of small cars. At some point, the road becomes unsafe at any speed. Leave the highway at the next exit.
Finally, be prepared to alter, delay, or cancel your travel plans if weather conditions require it. This is especially important for those who have little winter driving experience. Mixing a tight itinerary with winter driving conditions is almost always a bad idea; you'll be tempted to drive faster than is safe, or to drive instead of waiting out bad weather, in order to keep on schedule. If the hard deadline is approaching, don't race to keep it, but rather try to get somewhere where you can tell about the delay. If connections are unreliable or your battery is low, text messages often still work. Even if you cannot reach your friend, you might be able to call the emergency services, telling that you are safe. Even if you cannot, an unneeded search operation is better than a deadly accident.

Drive

Controlling your car

Stopping distance and speed

Reducing your speed is the best way to compensate for a slippery surface. If you can remember only one thing about winter driving, it should be slow down. Start carefully and test the surface by gentle braking until you know how slippery it is. Test frequently as conditions can change during a trip.
Driving on snow, and especially ice, requires extra stopping distance: 3–4 times greater than on dry asphalt is common. If your minimum distance to the next car is 3 seconds in summer, 5 or 6 seconds should be the absolute minimum on snowy or icy roads. Use extreme caution when going downhill.
Approach all intersections at a speed slow enough (20–30 km/h or about 15 mph) to be able to stop if there are other cars or pedestrians. Intersections are often more slippery. Turn lanes, or where one lane becomes two, may have had less traffic, resulting in more unmelted ice. Never try to run through yellow light traffic signals—especially when turning. Likewise, always check that other drivers are able to stop before proceeding through an intersection.
Corner at less than 30 km/h (18 mph). Practice this and find the speed where the car starts skidding, if necessary (but conditions vary).
When driving downhill, no amount of technical gadgetry (ABS, 4x4, ESP,...) will protect you against skidding. Gentle speed and high quality winter tires or snow chains are the only remedy. In really slippery conditions, it is better to downshift to reduce speed rather than to brake, as braking can cause the vehicle to move sideways (fishtail). Especially for large vehicles, do not drive in neutral or depress the clutch when going downhill: when the clutch/gear is reconnected, the wheels may have uneven traction and start sliding on one wheel, leading to a spin.
Even though a 4x4 is great for providing forward traction, it will not improve stopping distance.

Skidding

Skidding (sideways) is most likely to start with the driving wheels. So when driving a car with front wheel drive, a front wheel skid is most likely, rear wheel skid on a rear wheel drive, and on a 4x4 don't be surprised if all four wheels lose their grip at the same time!
A rear wheel skid is most difficult to control as the car tends to rotate, while a front wheel skid usually appears as straight ahead movement when you try to turn.
Avoid braking. You want to get your traction back. Braking with non-ABS brakes while skidding will easily cause the rest of the wheels to skid as well. For vehicles with ABS anti-locking brakes, do not pump the brake pedal if you start to skid.
It is very easy to panic and overcompensate, abruptly turning the wheels further when the vehicle initially fails to respond. This will quickly put you off the road, into a ditch or in the way of oncoming vehicles.
Disengaging the clutch is usually the best way to stop a skid in progress. A rear wheel skid can be counteracted by steering. If a front wheel skid started when trying to turn, you probably turned too sharply, try to get back the grip and then turn more smoothly.

Dangers

Especially slippery conditions

Temperatures around 0°C (freezing point) are generally the most slippery. The colder the road, the less slippery. Changes in temperature also make the road slippery.
When the ice and snow are melting or there is fresh snowfall on refrozen ice, the road surface is much more slippery than usual in the winter. Soft, melting snow (slush) is more slippery than ice. Steering (handling) is particularly difficult on slush, although braking distance is not unusually long. Cold snow is the least slippery.
Rain on a frozen surface, or rain in freezing temperatures, will form very slippery, invisible "black ice". Black ice can also form from the moisture in the air.
Watch out for the slippery ice or built-up snow between lanes.
Ice is more likely to form on bridges, overpasses, and ramps. Slow down when going over them, especially on the highway/motorway.
Ice on an otherwise dry road is also possible when there has been morning mist, such as in the shade of a forest. Be alert everywhere where there is likely to have been temperature differences.
Try to anticipate when you will need to use extreme measures, such as low-range four wheel drive, and shift before you are in trouble. Stopping entirely in a "traction condition" is the fastest way to get yourself stuck. If you see snow drifts, wet ice, etc ahead, take action in advance and you have a better chance of getting through it.
Be aware that in northern areas, late winter or early spring can be the most hazardous time, in particular on less heavily trafficked roads. In many places, roads are not cleared "down to the pavement" and there may be layered ice still on top of the road surface. The sun can glaze the ice, making it extra slick, or rain may puddle up on it if snow berms are preventing proper drainage. Wet ice is basically the slickest thing you will ever drive on and is extremely dangerous.

Deep snow

Deep snow – especially at just a couple of degrees under freezing – affects your ability to control your car, as the wheels have no direct traction against the road itself. It can be as dangerous as ice.
When driving through snow, the tires need to plow their way through the snow in addition to bringing the vehicle forward. Often the surface is slippery as well, and all this might be too much for the tires and leave you skidding when driving uphill or stranded if on an even surface. A combination of rear wheel drive, an empty trunk and bad tires will pretty much guarantee your getting into trouble when driving in snow. This is where snow chains are useful.
If you're driving on a highway where only the lanes themselves are plowed and there is snow or slush between them, move slowly when changing lanes. Suddenly moving across even a thin layer of snow or slush at highway speed can lead to the snow "grabbing hold" of one wheel, with disastrous consequences. This is why that uncleared area between lanes is called "the devil's strip" in some places.
It can be hard to know how wide the road is. Sometimes there are markings for the snowplow, but otherwise you have to be careful, especially when giving way for meeting traffic on minor roads, not to find yourself in the ditch.
If your vehicle becomes high centred on snow (meaning the wheels are no longer supporting the full weight of the vehicle), there is nothing you can do to simply drive out of the situation, so don't waste your time. You either need to dig out the snow beneath the vehicle, or pull it out with another vehicle or a winch. Digging may be of limited usefulness as well if the entire area has equally heavy snow, you'll just be stuck again moments after freeing it.

White-outs

In blizzard/white-out conditions, you may not be able to see anything through the windshield. Try rolling down the window and sticking your head outside. Then, find a safe place to get off the road and stay there until conditions improve.
In snowfall, main beam (headlamps full beam; high beam) may not be useful as the driver is blinded by light reflected from big snowflakes. Dipped beam (low beam), front fog lamps or even parking lamps may be better than main beam. But make sure full strength rear lights are used. If your vehicle has automatic headlamps that turn on in the dark, do not rely on them. Turn your headlamps on manually; these systems tend not to activate early enough in snowy weather, leaving it almost impossible for other drivers to see you.
Some areas are affected by snowsqualls – heavy snow that suddenly starts, stops, and changes in intensity, often accompanied by gusty winds – typically on the leeward side of bodies of water. Be aware that visibility can go from clear to almost nil in these regions with very little notice.

Things you may encounter

Change of route

If you miss your freeway exit, get off at the next one that has a re-entry ramp and turn around. Continuing on to a less-used alternate route in winter is foolish. Depending on region, there may be alternative usable highways, but stop off the freeway to evaluate the situation and plan your route.
If a road is closed due to the weather, there's a good reason for it. Don't even think of using local roads to get around the closure. Even if they aren't closed, they are probably in even worse condition. Waiting out the situation is just par for the course in winter driving.

Winter road maintenance

Trying to pass a snowplow or snow grader is almost always a bad idea. The blades can cast a ridge of wet snow or slush even on the overtaking (non-plowing) side, and hitting it at speed can make you skid. Besides, the road surface behind the snowplow is almost certainly better than in front.
For clearing freeways and other multi-lane roadways, echelon plowing is sometimes used: a fleet of snowplows clears all lanes simultaneously. It may be frustrating to be stuck behind an army of snowplows as they crawl down the highway, but trying to pass by cutting in between them is almost certain to result in a crash.
On undivided roads, snowplows often need to cross slightly over the centre line to clear the entire roadway. When meeting a plow, be mindful of where the edge of the plow blade is and stay well clear.
Salt is applied to roadways to melt ice and snow, but it loses its effectiveness when roadway temperatures drop below −12 °C (10 °F) or so. If a flash freeze happens, salt can actually backfire and make roads worse – it melts the ice and snow, which then refreezes when temperatures plummet. Be aware of this possibility.
Depending on road conditions, a mixture of salt and sand, grit, or gravel may be applied to the roads by specially-equipped sanding trucks to increase traction. Stay 10 m back from sanding trucks, as flying rock chips could crack or break your windshield. Sanding trucks often apply sand only to slippery areas, such as ramps, bridge decks and intersections, so you may get the impression that it's safe to follow more closely – until the sander is turned on.
Different jurisdictions or administrations may have wildly differing ideas about what constitutes adequate winter road maintenance. Also, different categories of highway usually receive differing amounts of attention. Watch for a change in conditions when entering or leaving a city or moving from one route to another.

Convoy driving

Convoy driving is used routinely in Norway and some other countries in difficult weather, particularly through mountain passes but also on other roads exposed to strong wind. Convoy driving means that drivers have to wait for a number of vehicles to line up and then follow a snow plow across the particularly difficult stretch of road. Only a limited number of cars are allowed, and each driver must never lose sight of the car ahead and never leave the convoy. In particularly difficult conditions only heavy vehicles (above 3.5 or 7 tons) are permitted. Waiting and slow driving means an hour or more is added to the trip. Convoys may run on a fixed timetable or departure may depend on the number of cars waiting.

Ice roads

In some regions there are roads made over the ice of lakes and rivers, even the sea, in the winter. Some provide road access to places otherwise inaccessible by car and some replace ferry connections. Locals may drive on the ice just for fun, although this is not without danger. Driving on ice by snowmobile is common, but not safe unless you know the waterway well.

Official ice roads are usually well maintained and secure at least in good weather, but do respect speed and weight restrictions. Speeding will cause cracks in the ice. Stopping on the ice is often a bad idea, as the weight of the car causes a local depression. In the worst case you will have water flow in and too steep a grade to easily get out. Check instructions for using the roads, there may even be peculiarities such as self service ferries over shipping lanes.

For unofficial ice roads, always get local advice. There will probably not be any obvious warning signs.

Driving on the ice where there is no road at all requires judgment and knowledge of local conditions. Having a ship open a lane between you and the mainland is no fun (and wind or a raise in water level can cause similar situations). Have a good big scale map and a compass. Snowfall or snowdrift can cause you to see nothing but snow.

Vehicles falling through the ice can routinely result in death of drivers or passengers, particularly at the beginning or end of the season where ice conditions are unstable.

Other advice

You need time in the morning to clean the car from snow and ice and have the cabin heated to avoid (or clear) misting on the windshield. In some countries police can issue a substantial fine if windows are not sufficiently cleaned. Mind the lights, mirrors and the air intakes below the windshield. Do not leave snow on the roof, as it can land on the windshield of the vehicle behind once you speed up, or on your windshield when braking.
Start the engine a few minutes before you are ready to go, especially if you have no engine heater (though this might be illegal in some countries, e.g., Germany).
You cannot drive at highway speeds with chains on. For most chains, the limit is 50 km/h (30 mph).
Check your rear lights regularly: you often need them also in daytime, as snow from the road reduces visibility, and the lights themselves may become covered. The check is especially important if you have LEDs, which don't melt even minor amounts of accumulated snow.
Pay more attention to signs – the road markings are obscured by the snow.
During snowfall at low temperatures, snowflakes may freeze onto heated car windows (notably the windshield). One solution to this problem is to switch off or reduce inside heating in the car, while still running the ventilation fan at high speed.
Although driving slower than usual is often advised, watch the locals and keep a keen attitude. Deliberately driving 10–20 km/h slower than traffic annoys other drivers and invites risky overtakes.

Survive

Accidents on trafficked roads

If an accident happens and the car is on a lane and cannot be moved, it might get hit by other cars. Remember that other cars will not be able to stop as quickly as on a dry road and the worse the visibility, the more likely it is that someone will collide with your car — this is how freeway pile-ups come into being. Depending on circumstances, you might want to get everybody out of the car and off the road. Having an injured person in the cold outside the car is often a bad idea, but you need to weigh that against the possibility of sustaining even more injuries if staying in a vehicle that oncoming vehicles might crash into. That said, sole cars very seldom catch fire and explode like in the movies.
A warning triangle (mandatory in many countries) should be placed 50–100 m behind the car so that other drivers have time to notice you and slow down. Especially if you have none, somebody should be placed to warn the traffic, if this can be done safely.
Fluorescent vests (also mandatory in some countries) are a very good way to make yourself noticed by other drivers in time, and they're usually cheap, so it's a good idea to have one or several of them in your car. At dark, you should at the very least have a safety reflector, otherwise you are almost invisible to other vehicles. If there isn't too much snow, stay next to the road.
If someone is more than lightly injured, call an ambulance (note that somebody seriously injured might feel OK). If somebody is unconscious, secure their breathing. The first aid kit should have a tool to cut the safety belt.
In case other vehicles are involved in the accident, check if there is someone who needs help. Every involved party will almost certainly need to contact their insurance company (though this varies between countries). In more serious collisions you should also call the police to at least direct the traffic and if needed investigate the accident.
You need to call a tow truck to tow your vehicle away if it can't be moved otherwise. Check beforehand whether your insurance covers this.

Stranded in a remote location

Advice for situations where you can anticipate a long wait:

Keep calm. Think. When the winter storm ends, you will be found.
Stay in your vehicle. It can provide enough shelter to save your life, better than any igloo or snow cave that you could make. Also, it's much easier for rescuers to see and to find, since cars are large and are always on or near roads.
If you must go outside for a few minutes (for example to clear the tailpipe), do not overexert. Wet, sweaty clothes cannot keep you warm. Clearing heavy snow is a common cause of heart attack.
If you must go outside in low-visibility conditions, use a line to tie yourself to the vehicle. Reeling in the line will lead you to the vehicle even in zero visibility.
Crack a window slightly, on the side away from the wind. Better to be cold and alert than warm and sleepy. There may also be toxic gases from the heater, if you are using it.
Make yourself easy to spot. Hang a fluorescent banner or traffic vest from the antenna or out a window during the day. At night, remove the cover from the dome light and turn it on; searchers can see it from a long distance. Do not turn on your emergency flashers unless you see or hear someone, as they are a much larger drain on the car battery. If there may be traffic on the road, you may have to use the emergency flashers, especially if you cannot trust your warning triangle (e.g. because of snowfall).
The vehicle will get cold when you shut off the engine or heater, and if you anticipate a long wait, you will want to save fuel. Even if you have a full tank of fuel (always advisable), you want to make it last for as long as possible. Using the cabin heater depletes the battery, so you will need to run the engine now and then if using the heater (or lights, or charging electronics). As starting the engine also eats battery, you should do this seldom and for longer times. Make sure drifting snow doesn't block the exhaust pipe. Check each time before restarting engine (unless obvious: not snowing and no wind), and shovel any snow out from the rear end as needed. Keep the radiator clear of snow so that the engine does not overheat.
You had those warm clothes handy, hadn't you? Perhaps also sleeping bags or blankets. Take them on before you get cold; it is much harder to regain all that warmth you lost. Don't have so much clothes that you sweat though.
To warm up, move around while inside the vehicle. This will also improve blood circulation. Loosen tight clothing. Put your hands in your armpits, between your legs, or rub hands together to warm them. Huddle together with other people in the car for warmth.
Protect any critical liquid medications such as insulin from becoming frozen. If there is no more heat from your vehicle, keep it next to your body.
Assuming no cell phone service, turn your phone on for 15 minutes every hour. Then turn it completely off to help save its battery. Don't waste the battery trying to dial numbers where there's no service. Rescuers can use portable receivers and direction finders to pick up its signal. However, even if they do, it's not possible to communicate with you over the phone. If battery power has become critical, leave the phone off after dark, as rescue efforts are often suspended sunset to sunrise. You should be able to charge the phone from the car battery by the round power outlet in the front panel.
When there is cell phone service, but the signal is poor or there is little battery, use text messages instead of calling or using the internet. SMS uses less power and does not need a continuous connection. Most land lines cannot receive SMS, so choose whom to text at which phone number carefully. Keep the internet connection off, as it uses much more power (and any Wi-Fi, bluetooth and whatever you may be used to having active).
Take care of toilet visits, eating and drinking and keeping spirits up. All practical matters are uncomfortable in the cramped car or the cold snowy environment, but ignoring your needs will not make them go away, and taking care of them sooner rather than later pays off.
Take turns sleeping so that there is always somebody watching and listening for rescuers.
If you absolutely must go outside, write your name, address, phone number, and where you are going on a sheet of paper. Leave the paper on the dash of the car.
Don't expect to be comfortable. Your goal is simply to survive until you are found.

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