Police say false information on Facebook pages warning people about alcohol checkpoints is scrambling the signals for drink drivers.
The pages are used to post details of the location of police breath testing units or warrant of fitness checks.
But assistant commissioner for road policing Dave Cliff says there are people posting incorrect information as a way to combat the "unfathomable" pages.
"It's a little surprising to us that people who could kill others could be warned by some individuals to try help them not get caught. [It] just doesn't make sense. Why would someone want to warn a potential killer and be responsible for a death? It defies explanation, really."
He says it's not possible to get all of the Facebook pages shut down, but what some users have been doing to counter them is helpful.
"Others will make up checkpoints and locations where there aren't and put in a lot of information which means potential offenders aren't warned because they've got no idea whether the information provided is genuine or not," Asst Cmmr Cliff says.
"I guess, as much as these things can hinder us, others can take advantage of them and help us."
He said police staff were not the ones posting the wrong information on the pages.
He does not believe those who set up those pages have thought through the consequences properly.
"I'm sure that if they thought that as a consequence of warning a drunk driver that person ended up killing or maiming some innocent person, they would think twice about doing it."
Facebook drink-drive checkpoint pages 'unnecessary' - AA
Meanwhile, the AA says the pages shouldn't be needed if people planned better.
Motoring affairs general manager Mike Noon says the warning system is unnecessary because people should be planning how they'll get home from a night drinking beforehand.
He says most drink driving incidents are the result of poor planning.
"We'd say they're unnecessary because people should not be drinking and driving, and quite frankly I don't want people, and I don't think our members want people, trying to use these sites to take a different route when they have been drinking and driving."
He says the pages hark back to a time in the 1970s where it "used to be a game" to try and avoid police.
"If you thought perhaps 'gosh, perhaps I could be a little bit over but I'll use this site to go a different way' then that's a really bad idea we reckon. If you feel that you're impaired or you know you're impaired then please don't drive. Please don't be on the roads with the other motorists who are driving sober."
However, he says it could lead to positive results in some cases.
"They could have a redeeming effect if somebody who was contemplating drinking and driving decided not to drink and drive because they felt they had more chance of being caught," he says.
However, Asst Cmmr Cliff doesn't think that sequence of events would be likely.
"If it means someone simply waits out a checkpoint and then drives after a checkpoint is gone while still under the influence of alcohol, they can still kill or seriously injure themselves of an innocent road user."