The sight of a sheet of frozen lake or pond is an invitation to many winter sports enthusiasts, from ice skaters and hockey players to snowmobilers and ice fishers. But that same ice can also be dangerous, and there are plenty of stories of people who have fallen through the surface and been trapped below. So, how thick does ice need to be to drive on?
Safe ice thickness can vary considerably by location and water body, as well as other factors such as age (newer ice is stronger), freeze / thaw cycles, proximity to the shore, and river currents. To be sure, always choose ice that has been measured by a designated authority on a regular basis -- such as staff at ski resorts, clubs or national parks, or government conservation officials. They should have access to quality ice measurement tools and procedures, as well as the training to use them correctly.
When checking ice, keep in mind that it's not just the ice itself that determines whether or not it is safe; it's the weight of your vehicle as well. Alberta's Workplace Health and Safety Guidelines say vehicles should be spaced 100 times the minimum applicable ice thickness. For example, a truck needs 12-15 inches of clear ice to safely travel on it. When parked, the constant load of a vehicle delivers an additional stress that can cause the ice to fail. So, it's important to check ice for strength every time you drive on it.