The Serious Crash Unit attended the scene, a police spokesperson said.
Police were making inquiries yesterday to speak with the driver of the vehicle involved in the crash.
International organisation Ironman Triathlon has responded with support for the triathlete, saying, "All of us at Ironman would like to extend our well-wishes to one of our own, Terenzo Bozzone, who was injured while cycling in New Zealand today.
"Our thoughts are with him and his family and we hope for a full and speedy recovery."
Fellow athletes have also sent good wishes, including cyclist Pedro Sanchez who wrote: "Sending my thoughts and prayers to an amazing athlete, friend and human being Terenzo Bozzone."
English triathlete Graham McKenzie said, "Sincerely hope Terenzo is ok. Wishing one of Triathlon's nicest guys a speedy recovery."
American triathlete Joe Maloy sent his thoughts and healing energy, and Olympian Nick Willis posted, "This is terrible. Hope Terenzo pulls through ok. Praying for you mate."
Ten-time Ironman Dave Carroll wrote, "Shocking news for the triathlon community. Thoughts are with this terrific Kiwi triathlete, hoping he makes a full and fast recovery.
"He was having an awesome year after finally winning Ironman NZ going just under 8 hours."
Bozzone has won 37 international titles, which includes 23 Ironman 70.3 or half-Ironman distance triathlon titles.
He is married to Kelly Bozzone, and has a son called Cavalo.
