During the first week fixed and trailer-mounted cameras were operating, December 1-7, a total of 3303 drivers were photographed breaking the law.

A total of 773,532 vehicles were checked at various locations around the state.

Minister for Roads Andrew Constance said the drivers caught using their phones were lucky they would receive only a warning letter.

When the period of grace ends at the start of March 2020, drivers will be fined $344, or $457 in a school zone, and incur five demerit points, or 10 during double demerit periods.

"At 60km/h if you look at your phone while driving for just two seconds, you travel 33 metres blind," Mr Constance said.

"It's dangerous, it's stupid and it needs to stop.

"About 500 drivers a day are getting pinged by these cameras doing the wrong thing.

"With double demerits starting Friday we need drivers to get the message and get off the phone, otherwise they risk killing themselves or someone innocent on our roads.

"I'd like to thank drivers doing the right thing. We have seen a two-thirds reduction in the non-compliance rate since we trialed the technology earlier this year."

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The camera pilot between January and June identified over 100,000 drivers illegally using a mobile phone while driving from the 8.5 million vehicles checked.

Executive director of Transport for NSW's Centre for Road Safety Bernard Carlon said independent modelling showed the latest addition to the state government's road safety program could prevent around 100 fatal and serious injury crashes over five years.

"We need to see a steep behavioral change from motorists to save lives," he said.

"While drivers caught on camera get a warning now, NSW Police will continue to issue fines for illegal mobile phone use as part of their regular operations," Mr Carlon said.

The mobile phone detection camera program will progressively expand to perform an estimated 135 million vehicle checks on NSW roads each year by 2023.