Jessica Simpson was riding her bike on a training session about 7am, heading north on Windang Rd.

She was riding in the left lane, about 1km south of Illowra Cres, when a male driver in the middle lane merged into the left lane.

Police said the car collided with the back of 21-year-old Ms Simpson's bike.

She was thrown off and was taken to Wollongong Hospital suffering a suspected broken pelvis, broken arm and cuts and bruises.

The young triathlete was due to compete in Florida in November at the World Half Ironman Championships.

It would have been her first competitive international event.

Officers from the police crash investigation unit attended the scene yesterday, taking measurements and interviewing witnesses.

No charges had been laid by the end of the day.

Former professional cyclist Josh Kersten said the Primbee Deviation was a notorious stretch of road for anyone on a bike.

"It's always been dangerous, especially in the mornings," he said.

"It's a big thoroughfare for people going to Wollongong and the speed limit is quite quick.

"It's a common area for accidents with cyclists."

Mr Kersten said cyclists needed to use the road for training even when bike paths were available because they rode too fast to be safe on paths.

"Athletes at that high level are travelling between 35 and 50km/h," he said.

"The road is very important to train on."

While Mr Kersten said he had never been in an accident while riding, there had been a few close calls.

A bike lane on the Primbee Deviation would help raise awareness among drivers that cyclists used that stretch of Windang Rd, he said.

"The road is there to be shared by everybody," he said.

"There is still room for cyclists."