One day many years ago, when I was in college, I sat with a friend who happened to be a graduate student in anthropology, sipping a beer and gazing out the window at the ebb and flow of university life on the busy street below.
As we watched, a guy came hurtling out of the alley just up the street, squatting on a sort of land-surfboard made by replacing the legs on a rectangular coffee table with roller skates. This young inventor/athlete flew off the sidewalk and into four lanes of traffic, narrowly missing or being missed by every vehicle on the road in an almost unbelievable demonstration of pure good fortune.
Unfortunately, when he reached the curb on the far side of the street his luck pretty much ran out. Since there was no way to steer it or slow it down, his contraption hit the curb square-on at full velocity, levering the table top over the front wheels and turning it into a sort of trebuchet, and the rider into projectile. He flew in a short, frantically-gesticulating arc across the sidewalk, through a plate glass shop window and into a display of leather handbags.