Several years ago, here in St. Paul, MN, there was a flatbed truck hauling a piece of heavy construction equipment—something like a bulldozer, I suppose; I have forgotten exactly what it was. It was held down by a chain. The truck turned a corner, the chain broke, and the equipment toppled off the truck and landed on a car that was stopped at the same intersection, crushing it and killing the driver.

I didn't see this. I only read about it in the newspaper, but it made a big impression on me. It made me wonder: Do truck drivers or construction workers (whoever loads the truck) really have any idea how big a chain you need to tie down a bulldozer? It seems to me, you'd need to be an engineer to make that kind of calculation. And even then, you'd have to make assumptions about whether the ground was level, how fast the truck would be moving, how tight a turn he would try to make, etc.

I think about this every time I see a truck loaded with anything heavy—construction equipment, bricks, steel girders, pipes....