My worst transportation story, that's easy, about 10 years ago I was riding my bicycle downhill on the sidewalk. The sidewalk had several dips like so:
I was having a blast zipping down and bouncing from those dips to the next until I saw this:
Note how it doesn't have a smooth transition; it's just concrete poking out at 90 degrees. By the time I saw this I was going pretty fast almost able to keep up with cars going 40mph and I couldn't brake in time nor could I swerve around it.
As you can tell by now I ended up running right into that 90 degree angle concrete barrier and flipped out landing hard. It apparently was a really hard landing because I barely remember anything happening afterward. The only thing I remember afterward is laying on a hospital bed getting stiches done on my hand and face and I had no idea how I got here. It was like a hangover moment.
Somehow a good samaritan saw me and drove me to the hospital thank the lucky stars!
And here's what I looked like, warning if you're squeamish don't look: