By Phil Mercer BBC News, Sydney

Sales of bicycles have doubled in Australia since 1998

Australia's love affair with the bicycle just keeps getting stronger.

Sales of new bikes are at record levels, and Australians now buy more bikes every year than new cars.

A desire to stay healthy along with concern about the environment and rising petrol costs are driving this pedal-pushing revolution.

"Parents are increasingly aware of the epidemic of obesity among children," said Ian Christie from Australia's Cycling Promotion Fund, which represents Australia's bicycle industry.

The nation's waistlines are bulging as never before.

A quarter of Australian children are overweight or obese. Within a couple of decades that figure could reach a whopping 50%.

Diet and exercise are key factors and youngsters are being urged to saddle up.

"Cycling gets kids fit, cuts traffic on our roads and reduces global warming," Ian Christie told the BBC. "Everyone's a winner."

Cycling groups want many more school children to ride to school.

I've had a fair few problems with traffic. You can guarantee every time you go for a cycle there's going to be a close call of some sort Jason Hill Cyclist

Those that currently do are very much in the minority, about 5%, despite most children living within a kilometre of the school gates.

Campaigners want that proportion to swell to 80% - up to where it was in the 1970s.

Climate change

Sam Powrie from the Bicycle Institute of South Australia, a long-standing advocacy organisation, believes that a new bike age is rapidly approaching.

"The Australian public has been profoundly influenced by the whole climate change debate," Mr Powrie explained from his office in Adelaide.

"The whole oil depletion phenomena is scaring the living daylights out of many Australians and they're desperately seeking more sustainable ways to live and the bicycle is a very obvious solution," he said.

A record 1.3 million cycles were sold in Australia last year and sales have almost doubled since 1998.

Jason Hill, a 31-year-old IT worker, bought his mountain bike a few months ago.

He described riding on Sydney's busy and often unforgiving streets as "a bit nerve-wracking."

"I've had a fair few problems with traffic," he said.

"You can guarantee every time you go for a cycle there's going to be a close call of some sort."

Road rage is a very big issue.

One Sydney driver said cyclists "were like rats" who had no place on the roads.

Battleground

As far as the law is concerned bike riders have as much right to be on the streets as motorists.

Some Lycra-clad cyclists have been accused of being arrogant and aggressive.

Activists ride naked to raise awareness of cyclists' vulnerability

"I think both sides think they own the road," said Jason Hill. "Everyone needs to relax a little."

He is not wrong. Australia's roads can be battlegrounds between those on two and four wheels.

In Adelaide, Sam Powrie said cyclists had been pelted with stale sandwiches and eggs.

One unprovoked attack last year left a close friend disabled.

"A very large lump of wood was thrown at him very forcefully at close range from a passing car by a group of young people," recounted Mr Powrie.

"He careened into a parked car. He had multiple upper body fractures, a major neck and head injuries and the disabling results of that continue with him today."

"It was a deliberate attempt to kill or maim," he said.

Highlighting the vulnerability of cyclists as well as environmental issues are key concerns for groups of nude activists.

In March, campaigners in Australia will join others in New Zealand and South America for a unique day of action.

"We're taking all our clothes off to say we're defenceless against vehicles that will hit us," said Marte Kinder, the coordinator of Australia's World Naked Bike Ride.

"Clothes aren't going to save our lives. We might as well be naked."

"When we ride without our clothes on we get respect," he said defiantly.