Competitive road cycling was supposed to help three-time world rowing champion Amber Halliday ease into retirement from elite sport.

Instead, this year's historic world championships in Melbourne and Geelong beckon after her outstanding win in the time trial at the Australian road titles.

The 30-year-old two-time Olympian was the only woman on Wednesday to average more than 41km/h over the testing 28km course at Buninyong, near Ballarat.

The nationals are not automatic qualifiers for the world titles or the Commonwealth Games that follow, but Halliday admits the win will make her rethink this year's plans.

"One of the reasons I got into cycling was to help the transition into normal life," Halliday said.

"After this performance today, I'd be crazy not to try to have a bash through this year and try to be selected in that (worlds) team.

"It's long way away, Geelong, but how good would it be to be there?"

The September 26-October 3 world road championships will be the first time that a southern-hemisphere country has hosted the prestige event.

Halliday, an Adelaide sports journalist, rowed at the Athens and Beijing Olympics, but said competing in London on the road was not a major priority - yet.

"You'd be crazy not to want to go if you could, but it's not the be-all and end-all of my life at this stage," she said.

Halliday is among a growing number of elite rowers who have switched to road cycling and specifically the time trial.

Until her win, the best example was Amy Gillett-Safe, who died in a 2005 traffic accident while training in Germany.

Halliday's first serious race was the time trial at the nationals last year, where she showed her potential with a surprise fourth place.

Sally Robbins (24th) and Olympic champion Drew Ginn (sixth) were other well-known former rowers competing in Wednesday's time trials on day one of the nationals.

Indeed, all three placegatters in the elite women's time trial on Wednesday have come to cycling from other sports.

Halliday clocked 40 minutes and 47 seconds, averaging 41.02km/h, and 2008 national champion Bridie O'Donnell was next in 41:01, while Carly Light took third in 41:59.

O'Donnell is also a former rower and finished the Hawaiian Ironman triathlon, while Light used to be a distance runner.

Last year's silver medallist Alexis Rhodes was a pre-race favourite, but she had to retire after two punctures early in her ride.

Adding insult to injury, race judges fined her $100 for her furious reaction to the misfortune.

"I may have had a bit of a dummy spit ... there was a bit of bike throwing and a bit of a tantrum, but I'm over it now," Rhodes said with a wry smile.

Also on Wednesday, world track champion Cameron Meyer scored his first senior national road title with a convincing win in the men's 39km time trial.

Former junior world track champions Rohan Dennis and Josephine Tomic took out the under-23 time trials.

The nationals continue on late Thursday afternoon in Ballarat with the under-23 and senior criteriums.

AAP