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A person scraping ice from a car windscreen

Driving in Sub-Zero Temperatures

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The Ice Road Truckers know only too well that at the height of winter temperatures out on the Ice Road can fall as low as -40 degrees Fahrenheit (-40 Celsius to us Brits, as the two scales come into conjunction at that temperature). The terrain can be tough enough on its own but those sub-zero temperatures can take their toll on both vehicle and driver alike.


We all know that it's harder to start a car in cold weather but many of us don't really know why that's the case. The main culprit is the battery. At 0 degrees F (-18 C) a fully charged normal car battery has less than half its potential starting power. This is because the cold actually slows down the chemical reaction within the battery. Motor oil is also thickened by low temperatures and so it requires more power to physically get the engine moving which, in turn, puts more strain on the battery. Heaters are installed on vehicles that are regularly parked in sub-zero temperatures to ensure the battery stays warm enough to function properly.


Brake fluid is hydroscopic – meaning that it absorbs moisture from the air. Left unchecked, brake fluid's freezing point rises over time due to the water content that has been absorbed. This means that the brake lines themselves can – in theory – freeze solid, making stopping impossible. This is very rare and would require a large water build up which modern fluids and mechanics are designed to prevent. A much more common cause of brake problems in normal cars in sub-zero temperatures is ice building up on the brake pads and freezing them in position, preventing the vehicle from moving. On the IRT's trucks sealed covers around the break drums prevent moisture from getting in where it could freeze things up.


An average car tyre inflated to 30 psi on a 70 degree F (21 C) day will drop to below 20 psi if the temperature drops to 0 F (-18 C). What may have been a minor puncture in normal weather can quickly turn into a flat tyre as the rubber contracts in cold temperatures, literally squeezing the air out. Specialised winter tyres with extra deep tread and chemically engineered rubber that remains flexible at low temperatures keep the Ice Road Truckers rolling along.


Inside the truck, the drivers too need to be kept warm enough to function, of course. One of the lowest documented body temperatures from which anyone has recovered was 55 degrees F (13 C) in a near-drowning incident in Sweden in 2010, but hypothermia can set in at anything less than 95 degrees F (35 C). Until recently it was necessary for a driver stopping on the Ice Road to sleep to keep his or her engine idling in order to keep their in cab heaters going. Typically one hour of idling would use a gallon of fuel – something which you really do not want to run out of on the desolate Ice Road. New specialised heating systems installed in many of the cabs earlier this year, however, no longer require the engine to be running and offer almost twenty-four hours worth of warmth on a single gallon of gasoline.