At least 100 motorists have received a $320 fine for driving in a bus lane over the Sydney Harbour Bridge, despite being diverted into the lane by NSW road authorities.

But following questions from the ABC, Roads and Maritime Services confirmed it had incorrectly issued more than 100 fines to the motorists over two nights in July and would withdraw the infringements.

Southbound drivers crossing the Harbour Bridge were directed by the Roads and Maritime Services into a single bus lane because of roadworks on the nights of July 4 and 5.

Those motorists were then sent an infringement notice saying an automatic camera had captured their vehicle illegally driving in the bus lane, which incurs a $319 fine and one demerit point.

Paul Gill, who is from Newcastle but was visiting Sydney, was one of the drivers to receive a notice and said he only questioned the penalty because he rarely drove across the Harbour Bridge and recalled the roadworks.

He said he challenged the infringement and requested the photo of his car taken by the automatic camera.

"I thought, hang on, this doesn't sound like something I'd do," he said.

"In the photo you can see the car I'm driving and you can see a train of about a dozen taillights in the same lane ahead of me."

He said when he spoke with the RMS, he was told there are no checks to see if there were roadworks in the area when fines are issued.

"I asked if anyone in Roads or the SDRO [State Debt Recovery Office] would examine those fines and was told 'not unless those drivers lodge reviews'," Mr Gill said.

"Presumably if you get 100 fines in an hour you're going to go through and say 'hang on, what's happened here?'"

Mr Gill said he had concerns at the time for those drivers who would not challenge the fines they receive.

"What concerns me is there are a dozen cars ahead of me, and unless those drivers remembered why they were in the lane, they would have paid the $320 fine without realising it," he said.

"If you're someone who goes across the bridge three or four times a day, you see the fine and go, 'maybe I did do it?'

RMS NSW says fines and demerits will be 'reversed'

In a statement, an RMS spokesperson said the fines and demerit points would be reversed.

"Roads and Maritime Services works closely with the Transport Management Centre to inform motorists of changed road conditions while using community feedback to identify errors and minimise the instances of fines being issued incorrectly," the spokesperson said.

"When an infringement is issued in error all fines and demerit points are reversed.

"Roads and Maritime Services apologises for the inconvenience."