The Mercury reported last week that the northbound camera on the motorway at Gwynneville was the region's biggest moneymaker for 2016 with $1.8 million.

The camera is historically the highest earner in the Illawarra and regularly passes the $1 million mark.

Centre for Road Safety’s executive director Bernard Carlon said factors like crash history, road geometry, traffic volumes and the number of access points go into determining speed limits.

“The 80km/h speed limit on the M1 Princes Motorway at Gwynneville is considered appropriate due to the significant vehicle volumes, road geometry and proportion of heavy vehicles,” Mr Carlon said.

However, he said Roads and Maritime Services was conducting a speed zone review of the adjoining 90km/h section of the M1 Princes Motorway just to the south of the camera location.

Mr Carlon said the cameras aimed to reduce crashes, not catch speeders.

“Our aim is to slow drivers down, not fine them, which is why speed cameras are clearly signposted and all locations are published on the Centre for Road Safety website,” he said.

“In the five years before the camera was installed at this location, there were 15 casualty crashes resulting in 32 injuries, at a cost the community of $3.82 million.

“From 2011 to 2015, after the camera was put in, there have only been four casualty crashes resulting in four injuries, at a cost of $0.48 million.

“That’s a 73 per cent decrease in casualty crashes, and an 88 per cent decrease in casualties. This shows the camera is doing its job.”