IT pays to be sneaky.

Queensland's covert speed cameras have snared more than 17,000 motorists in the five months they have been operating - catching 10 times as many speeders passing them as their fixed counterparts.

The cameras - hidden in beaten old bombs, utes and other unlikely vehicles - have fined 21 drivers for every 1000 passing them since they were introduced in April, compared with less than two per 1000 for fixed cameras.

In August, the number of drivers fined soared to 9300 as the covert cars were deployed almost around the clock. Last month the cars spent a whopping 588 hours in operation, or the equivalent of having one covert car out 24 hours a day for the first 24 days of August.

The next highest was the first month they were introduced, April, when 3357 motorists were caught.

And they look set to spend more time fining motorists, with police given the green light to use them for as much as a third of their speed camera work.

They have so far caught an average of 16 speeding vehicles for every hour they are deployed.

Police Minister Neil Roberts was unapologetic about the blitz.

He said the fixed camera detection rates had dropped a staggering 80 per cent in some places as drivers learned not to speed in those areas.

The next step, he said, was to convince Queensland lead foots they could be caught anywhere, anytime, by the covert cameras.

"We've got a culture of speeding in this state and this country and we've got to break it," Mr Roberts said. "Covert speed cameras really fit in with that - they can be in any street at any time. That mindset that the police could be on any road does get people to slow down.

"The target would be that no one gets done for speeding."

Mr Roberts said fixed speed cameras had resulted in a dramatic drop in the number of speeding drivers.

On the Bruce Highway at Burpengary, the number of speeding motorists has dropped by almost 90 per cent since the fixed speed camera was introduced in January 2008, from 8.26 per 1000 vehicles to 1.05 per 1000 now.

Cameras at Southport and Broadbeach are still detecting two speeders for every 1000 vehicles.

knowlesd@qnp.newsltd.com.au