A trial of "world-first technology" that snapped photos of every driver who passed cameras on two Sydney roads, irrespective of whether they were in the wrong, has raised concerns from the state's Privacy Commissioner, internal government documents show.

The state's transport agency hired technology firm Acusensus for a three-month pilot early this year, which was aimed at photographing drivers who were illegally using mobile phones near the M4 motorway at Prospect, and Anzac Parade at Moore Park.

The high-tech system captured images of all passing drivers and number plates, which in the first 25 days of the trial amounted to 2.1 million vehicles.

About 10 per cent of all "sightings" in January were sent for "human pre-verification" by staff at Acusensus, internal documents released to Nine News under freedom of information laws show.