How thick...does ice have to be for cars to race on it? The CBC had video of two cars sinking on the raceway made of ice.
The St. Lawrence River turned out to be a river and not a road. There was footage from a dash camera inside one of the cars that went under the ice.
"Partway through the competition, two cars are seen driving behind two other cars when they started to sink through the cracked ice.
The drivers of the vehicle that captured the footage quickly got out of the sinking car. The driver, Patrick Renaud, was captured on video walking on top of the hood of the car to get to safety. Vincent Noel was the second driver who plunged into the river." He got out too.
Here's the footage. It turns into a big hole.
How thick should ice be? Destination Ontario tells us that for driving on the ice, you're looking for a minimum of 30 centimetres (12 inches) or more for a light vehicle, according to the Ontario Ministry of Natural Resources. They have this caution: remember this is 30 centimetres of blue ice, so double that thickness if the ice is white or opaque.
There were many cars racing so I expect there would be a few calculations to know the needed depth. Articles talk about the speed of the vehicle - the formula explained in Wikipedia is the Gold Formula. | 
