More than 75,000 vehicles were inspected by a single mobile phone detection camera used in the Hunter for nine days over summer.

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The camera, on the Pacific Highway at Twelve Mile Creek, caught 370 drivers using a mobile phone.

The transportable camera was used for nine days between December 1 and January 31. Had it not been for a grace period that is set to conclude on Saturday, the offending drivers caught would have been issued more than $125,000 in fines.

Instead they were sent warning letters detailing the offence and urging them to change their behaviour.

The penalty for an offending driver, which will kick in from Sunday, is five demerit points and a $344 fine, rising to $457 in a school zone.

More than six million vehicles have been checked and more than 20,000 warning letters issued statewide since the new cameras were rolled out on December 1.

Centre for Road Safety executive director Bernard Carlon said the cameras were being moved regularly to avoid their locations becoming well known.