The 36-year-old Martin said he will call it a day after taking part in Sunday's individual time trial and competing in the mixed relay scheduled for next week.

The road world championships kicked off Sunday in the Flanders region of Belgium.

Martin had one year remaining on his contract with Jumbo-Visma but had informed the team's management after the Tour de France that he would not continue.

Martin crashed out of the three-week event in July during Stage 11, when he had to be stretchered off in an ambulance.

Martin had also crashed in the Tour's opening stage after a careless spectator brandished a large cardboard sign while leaning into his path.

"The bad crashes this year have also caused me to question whether I am ready to continue to face the risks that our sport involves," Martin said.

"I have decided that I do not want to, especially since race safety has not improved despite the many discussions about courses and barriers."

Nicknamed "Der Panzerwagen" for his enormous power, Martin also won the one-week Paris-Nice in 2011 and has 10 German time trial titles to his name.

"Cycling has been a large part of my life for a long time, with highs and lows, big successes and losses, crashes and comebacks," Martin said. "What many young riders dream of, I have achieved."

Australian Associated Press