The sign was spotted on Camden Valley Way in Elderslie, a suburb in Sydney's Macarthur Region, on Saturday amid wild wind and torrential rain that smashed large parts of NSW.
"Speed camera ahead", the sign positioned at the side of the northbound lane read, with a smiley face also featured.
While many expressed appreciation for the cardboard sign, which was attached to a chair, others were significantly peeved at the creator's cheeky act, which was shared by a community member on Facebook.
Debate over 'legend' who left speed camera sign
Some applauded the bold act and claimed it had saved them from potentially incurring a "revenue raising" fine.
"We drove past that twice today. Whoever put that out is a legend. It's just revenue raising," one person said in a comment, adding wet conditions meant more drivers were driving under the limit.
"That sign saves lives, that [police] car sitting there waiting raises revenue," another person argued.
Someone else wrote: "Not all heroes wear capes."
"Who ever did this you sir or madam go to the top of the class. Pass go and receive good luck for the rest of your life," another said.
Others were fast to condemn the act and argued drivers caught speeding in Saturday's dangerous conditions deserved to be fined.
"Anyone speeding in this weather deserves more than a fine," one wrote.
"No one should be speeding in the weather anyway. They deserve to get caught if they are," another said.
"Don’t speed and you wouldn’t need a sign. This person needs the fine," a third wrote.
Narellan police confirmed to Yahoo News Australia there was a speed camera in that location.
The Department of Transport and NSW Police were unable to confirm if erecting the warning sign was a punishable offence.
However there are rules about flashing headlights to warn other motorists of an upcoming speed camera.
Flashing high beams technically is not illegal, but using them inappropriately carries a maximum penalty of $2200 if the matter is taken to court.
Police in NSW can issue an on-the-spot fine of $112 to drivers caught using high beams inappropriately.
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