Known as the Kentucky Kid, he had his first race at the tender age of five.
Throughout his club racing career he regularly had to start from the back of the grid as he was so short he needed someone to hold his bike upright as his feet could not touch the floor.
Born in Owensboro, Kentucky on July 30, 1981 he followed older brother Tommy on to the racetracks of America.
Nicky Hayden of the US won the Moto GP world championship in 2006, narrowly beating Valentino Rossi.
He raced for Honda and Ducati in his Moto GP career from 2003 to 2016, recording three race victories and 28 podium finishes in 218 races.
Judicial authorities have opened an investigation into the incident and questioned the 30-year-old driver of the Peugeot.
Hayden won the Moto GP title in 2006, finishing narrowly ahead of Italian great Valentino Rossi.