It's not the post-apocalyptic competition featured in the Mel Gibson movie.
Instead of "two men enter, one man leaves" ...
It's more like "around 100 men and/or women enter, around 100 men and/or women leave... perhaps with some scrapes and bruises."
A write up on this wild, anarchic race is featured on the Changing Gears website by WBEZ's Robin Amer.
Robin writes about how the organizers unearthed an abandoned velodrome in Detroit's Dorais Park:
It was literally unearthed by one of the city’s vigilante lawn-mower gangs — people who mow the lawns at city parks because the city cannot afford to do so. The velodrome, on the city’s east side, was repaired by racing enthusiasts who cut down trees growing in its center and invested thousands of dollars of their own money and over 4,000 lbs of concrete fixing its surface. And now, it has come back to life as home to a variety of competitions.
When asked who the sanctioning body for this race is, organizer Andy Didorosi replied:
We are. We're the only sanctioning body in the world for zany two-wheeled party racing on abandoned Velodromes. :) Sanctioning bodies are silly.
Here's a video of last year's race. I like how the victor, instead of doing a lap with a checkered flag, does a lap with a torn-off portion of a Pabst Blue Ribbon box.