Hmmm, where to start. 
1. My dad. He has macular degeneration, was legally blind in one eye, couldn't see out the other, only has periferal (sp) vision, but somehow the License Bureau idiots in Oklahoma gave him another drivers license. :Q:| So he kept driving. He and his SO were travelling all over the country in a van towing a 20 foot trailer. He would drive and his SO would read the signs and help watch during merging. :Q:Q:Q 
Fortunately for all on the road, he no longer drives. (that I know of). Well, except for tooling around on a Honda scooter that can do 45mph. He's only almost hit 1 pedestrian so far. :Q
2. Potholes in Kansas. We were coming back to Kansas City in an International, running bobtail, hit a pothole that threw me up against the top of the cab, and broke the welds on the external battery mount. Fortunately we were able to stop and make repairs. :Q
3. Saw a hotshot on a crotch rocket zoom by me doing 75mph+, doing a wheelie at the time, on the highway, moderate traffic. :Q 
4. Boom truck I was driving, trailer hitch broke, large air compressor on wheels takes off down the highway. Fortunately, the only thing it took out was a light pole. Which the city charged the replacement to the company I worked at. Which then turned around and sued the welding shop that had fabricated the hitch (same day we picked it up it broke)
5. Dump truck, full of gravel, towing a backhoe on a trailer, lost the brakes. No emergency brakes, no pumping them up, nothing. :Q Fortunately, I wasn't on the highway, only doing about 40mph, the light turned green right before I got to it, no one in front of me, steep hill after the light. Finally got it slowed down enough to pop into granny gear, then crept to the nearest place I could pull off. :Q
6. Seen numerous trucks/cars pulling trailers that had too much weight forward, lifting the front of the vehicle almost to the point the tires lifted. Very little steering capabilities at that point. :Q