The Science of Driving on Ice

Keeping drivers safe on frozen water isn’t left to chance

YELLOWKNIFE, Canada Driving on an ice-covered lake—it's a fundamentally scary proposition, right? What if you fall through? Fortunately, the chances of that happening are somewhere between slim and zero on a properly prepared ice course, but that's not just the natural order of things. A lot of work goes into turning an ice-rimmed lake into a suitable racetrack—or highway for that matter.

Near Yellowknife, in Canada's remote Northwest Territories, Volkswagen showed us some of the science that goes into creating massive ice highways like those you've seen on shows such as "Ice Road Truckers"—or, for locals, routes like Dettah Road, which traverses a portion of the Great Slave Lake's 300-mile span, enabling vehicular access to areas reachable only by boat most of the year.

Preparation to get the ice strong enough to drive on safely begins as soon as the ice is thick enough to support the plow vehicles. The road teams start by clearing the snow from the path the road will take. This strips the ice of the snow's insulation, letting the biting wind freeze the path even more deeply than the surrounding ice. If the process isn't proceeding quickly enough, workers can bore a hole through the ice, insert a pump, and draw up lake water to refreeze on the surface. In this way, they can add 6 or 8 or more inches of ice to the road surface in a single day.

Sixteen inches of ice is the minimum you'd want to drive on—though locals sometimes drive on less, not always successfully. At that level, the ice can safely support large vehicles, vehicles with trailers, and multiple vehicles passing at once. More ice is needed to handle the constant abuse of a public highway, however, and when it comes to ice driving schools, you'll rarely be on less than 4 feet of solidified lake.

Still a bit creeped out by the thought of sinking to the frigid bottom? Just remember, hearing the sharp pop of cracking ice is a good thing—it's when the cracking stops that it's time to get out and run. Why? Because it means the piece you're on has broken free and is no longer supported by the surrounding ice.