Adelaide drivers claim they were fined even though they weren't speeding

An Adelaide driver who is challenging a $900 speeding fine is among a growing number of motorists claiming they have been wrongly penalised.

When Keith Beaumont returned from holidays, he found a letter stating he was driving 82km/h in a 60km/h zone in Crafers.

He'd taken the South Eastern Freeway as he made his way to the airport last month

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Beaumont said he remembered the speed limit was 90km/h but the fine suggests it was reduced to 60km/h for roadworks.

"It's just way over the top, I think, I just haven't paid it," he said.

"And I'm sort of glad I haven't now because I found out a lot of people are in the same boat."

Adelaide residents took to social media to claim they received fines despite driving under the speed limit.

Many claimed they copped multiple penalties, some as many as eight, each costing five demerit points and leaving them more than $900 out of pocket.

The number of claims sparked an investigation by the state's transport department.

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"It's quite possible that dozens to hundreds of people have been using this freeway and may have accidentally been fined when they weren't actually speeding," opposition spokesperson Vincent Tarzia said.

Transport Department CEO Jon Whelan said footage from the transport management centre would be reviewed.

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The speed cameras are electronically connected to the variable speed signs along the freeway

"The actual red light camera cannot activate or expiate a notice without it being linked to the variable speed sign," Whelan said.

An investigation is underway with results expected within the next two days.

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