According to Road Safety Minister, Jennifer Rankine, no single fixed roadside camera in the state generates more than $1 million a year in revenue.

The Minister has also defended the use of the cameras saying that since they were installed in 1988, the number of drivers exceeding the speed limit by 10km/h or more has fallen.

Adelaide would have six new fixed cameras in operation by September, Ms Rankine wrote in a letter to independent MP Bob Such.

He had written to her on behalf of a constituent questioning the number of cameras and asking who was responsible for deciding where they were placed.