Typically, the fisticuffs are confined to the pits and paddock, safe from prying eyes of the vast majority of the crowd. But spectators in Jeffersonville, Indiana recently got a show when one racer tore off across the infield of the Sportsdome Speedway to blindside another competitor at race speed. Fortunately, "race speed" in this instance is somewhere in the neighborhood of 45 mph and it doesn't appear anyone was hurt from the actual crash.
But that's not where the blood-boiling ended: both machines came to a stop, both drivers jumped from their cockpits and began beating the life out of each other before other racers and officials came to intervene. You can't make this stuff up. Check out the grainy video for yourself.