Katusha's Marco Haller shows how a properly fitted helmet should sit on the head. (Getty)

Katusha's Marco Haller shows how a properly fitted helmet should sit on the head. (Getty) Source: Getty

A global study of more than 60,000 injured cyclists found helmets reduce the chances of serious head injury in a crash by up to 70 per cent.

An Australian mathematician is behind a global review into bike helmet safety.

It’s the world’s largest review into bicycle helmets, and was presented at the international injury prevention conference Safety 2016 in Finland.

The review found wearing a helmet in a crash significantly reduces instances of serious head injury, skull fractures, facial injury and brain damage.

Report author Dr Jake Oliver said the findings also rejected controversial claims that helmets caused neck and spinal injuries.

Leading Sydney Neurosurgeon Dr Timothy Steel was not surprised by the review’s findings.

“Most patients who have head injuries don't sustain such bad injuries because they were wearing a helmet,” Dr Steel said.

“The helmet design is so good now that it really does protect the skull very well."

Bicycle enthusiast James Demetrio says he owed his life to a helmet after falling off his bike and hitting his head on a roadside curb as a teenager.

"Luckily I wore one that day and luckily the helmet saved my skull," Mr Demetrio said.

Now the manager of Centennial Park Cycles hire store, Mr Demetrio has noticed many international visitors don't share his view on bicycle safety.

"Many international visitors come and hire a bike and are not used to the helmet laws in New South Wales, and reluctantly they've had to wear a helmet."

While helmet use is considered mandatory in many countries, Australia and New Zealand are the only two jurisdictions that enforce universal helmet use.

Despite the review’s finding, not everyone believes helmets should be compulsory In Australia.

BIKESydney spokesperson David Borella says compulsory helmet laws are turning people away from the sport.

"Mandatory helmet law is holding back the uptake of cycling. We need to get rid of the law and let it to people to choose whether they want to wear a helmet or not," Mr Borella said.