During the Trans-Am Weekend in 1990 I tangled with another driver on the main straight at Mosport. We were both taken to the track hospital but checked out OK. So much debris was on the track after he landed the race was stopped. As the guy went over me his tire left a little souvenir on my helmet. For illustration the image at left is Ralf Schumacher launching over Rubens Barichello at the 2002 Austrian Grand Prix.  When Formula cars touch wheels the trailing racecar can launch.