An amateur cyclist involved in a "freak" racing accident in Tasmania's north-west is undergoing emergency surgery.

The family of Shamus Liptrot have rushed from South Australia to the Royal Hobart Hospital, where the 17-year-old has remained in an unconscious state.

Mr Liptrot was one of seven cyclists who crashed at high speed during the final stages of a heat race at the Devonport Carnival on Saturday night.

The scholarship-holding rider for the team South Australian Sports Institute - Team O'Grady was flung over a fence before he hit a light pole.

"It was a horrific accident," Cycling SA director Max Stevens said.

"He was catapulted off his bike, he went for about 10 metres, slid across a fence and then hit a light pole.

"... He has gone over the handlebars. If he had gone left he would have been on the grass but he went right - that's the freakishness of it."

Mr Liptrot was first taken to the Burnie Hospital suffering skull and jaw fractures, a broken leg, and also from a loss of blood, before he flown to Hobart.

"He's having an operation, as we speak, to remove some skull bone from his brain area," Mr Stevens said.

"Whether that operation takes three hours or six hours, we're not too sure, and if that operation goes to plan, doctors will also operate on his broken leg to repair that."

Mr Stevens said his thoughts were now with the Liptrot family.

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