Ice safety: How thick is safe?
2 inches: one person on foot
3 inches: a group of people traveling single file
7.5 inches: supports a two-ton car
8 inches: supports up to a 2.5-ton light truck
10 inches: supports up to a 3.5-ton truck
12 inches: heavy truck 7 to 8 tons
15 inches: holds up to 10 tons
20 inches: holds up to 25 tons.
Source: Maine Department of Inland Fisheries and Wildlife