2006 MotoGP champion Nicky Hayden has tragically died from injuries sustained in a road traffic accident last Wednesday.

The 35-year-old American, who switched to the World Superbike Championship in 2015 but made two final MotoGP appearances last season, was hit by a car while training on his bicycle at around 2pm near the Misano circuit in Rimini, Italy.

Hayden was transported to a local hospital with 'extremely critical' head, chest and pelvic injuries, then on to the intensive care unit of Maurizio Bufalini Hospital in Cesena.

Sadly, there would be no improvement in his condition and the hospital has announced the worst possible news.

Although Hayden only won three MotoGP races, he was every inch a champion, both on and off the track.

Hayden was hard but fair in his battles with fellow riders, took pride in never giving up until the chequered flag and set new standards of professionalism when representing his team, sponsors and sport as a whole.

The #69's exciting dirt-track style combined with a relaxed, welcoming manner, Hollywood smile and Kentuckian quips helped make him an instant hit with fans and media alike from his 2003 MotoGP debut.

If points were awarded for the number of autographs signed, or waving and pulling wheelies for the fans whether finishing a session in first or last place, Hayden would have been a world champion many times over.

His fellow competitors held him in equally high regard. A factory rider for both Honda and then Ducati, Hayden was team-mate to two of the sports all-time greats - Valentino Rossi and Casey Stoner - winning their respect and friendship.

Reacting to the news of Hayden's accident, Rossi called the #69 "one of the best friends I've ever had in the paddock", despite being the rider who ended the Italian's run of five consecutive MotoGP titles in one of the sport's biggest upsets at Valencia 2006.

A lack of competitive machinery and a serious wrist injury dogged Hayden's final years in MotoGP. But the Kentuckian fought back to join an elite group of riders to win both MotoGP and World Superbike races, after switching championships at the end of 2015.

Hayden was competing in his second WorldSBK season, with Ten Kate Honda, when the fateful accident occurred just days after the Imola round.

And now a bright star has gone out.

Having spent almost his entire life racing motorcycles, Hayden was fully aware of the dangers - Daijiro Kato died in Hayden's very first MotoGP race at Suzuka in 2003, and the American was on track when Marco Simoncelli was killed at Sepang in 2011.

But to lose his life away from the race track, without even the caveat of 'doing what he loved most and knowing the risks', seems especially cruel.

Hayden's death also closes a chapter in US motorcycling history. The former AMA Superbike champion had been the last American competing in MotoGP and now also World Superbike.

We join the whole motorcycling community in offering our deepest condolences to Nicky Hayden's family - especially his father Earl, mother Rose, sisters Jennifer and Kathleen, brothers and fellow racers Tommy and Roger, and fianc? Jackie - and his many friends at such a difficult time.