I've seen stupidity at its best while driving truck. Women putting on make-up, guys reading novels or papers from work, couples engaging in several different types of sexual activity, people driving with the seat leaned all the way back and both feet out the window...then, some of the stupid shit people try to haul in/on vehicles obviously not meant to be used that way...sofas on top of small cars, boats stuck in the back of pick-ups, (not just small aluminum fishing boats...large boats that hung out of the back so far they had to be tied down just to keep them from tipping out, (yep, you guessed it, they often don't stay put) all kinds of crap that's not secured in ANY way, which usually ends up in the roadway, where the idiots may try to run into traffic to save Aunt Myrtle's pillow.
Sadly, commercial drivers aren't exempt from stupidity...in the bay area, a large percentage of the truck drivers are immigrants, and have ZERO idea how to drive at all, let alone drive a big rig. I worked in one gravel pit near Milpitas, and it was very common for them to pull into the pit to get loaded, then pull away with a belly-dump trailer full of rock, gravel, sand, whatever, and the dump gates on the bottom are still open or only partially closed...We used to get called a couple of times per week by the CHP to send someone to clean up 40 tons or rock that one of them had dumped all the way down Scott Creek road and onto 680. We billed the driver about $400/hour for the clean up. If they didn't pay, they were banned from all the company's gravel plants...and we had 75% of them in the east bay...
I've seen semis stuck under overpasses, gas station canopies, in viaducts, on railroad crossings plainly marked "NO TRUCKS," loads dumped all over the shoulder, main traffic lanes, on off/on ramps, trailers sitting in the middle of the road where they fell off the tractor because the moron couldn't be bothered to actually check to see if the fifth wheel had latched...
People seem to leave their brains at home when they get behind the wheel of a moving vehicle...