In the old days we had big balls. It was kind of by guess or by "oshit" Nowdays they have the Ice Doctor go out and test the Ice before we build ice roads that are engineered to haul over (of course those engineers never had to stand out in the middle of the Artic Ocean and listen to the ice pop and crack while pulling a 4600 Manatowc to a drill site). Some of those roads are over land and some over the Artic Ocean. Thats kind of nice, as the loads sometimes exceed 1,000,000#. We lost several operators through the ice during the early years of building Americas oilfield in Prudhoe Bay AK. We haul everything from 350 ton cranes to the Sub-structure and related pieces of oilfield drill rigs over these ice roads. Some of the tractor/trailer combinations weigh 3 to 400,000# empty! Someday when I have time I will scan some photo's and see if this dumb old truck driver can figuare out how to get them uploaded.