I remember seeing a sheet of plywood blow off a truck one time when driving up I-91 to go back to college in Mass. It sailed right over the top of my car like a floating leaf. Could see it through the sunroof glass. Crazy.
A few months ago, I drove through a construction zone on I-64 here in Virginia. There was debris all over the road, some large. Looked like glass or rock or something, and I figured it was related to the construction. At the next emergency pullover, there was a tractor trailer hauling a load of granite counter top material. Looks like a strap broke and he must have lost numerous slabs. I would have been curious to see that action unfolding, but on second thought, I am glad I missed it.