In June this year, the fixed speed cameras between the Towradgi Road and Railway Street intersections were switched off.

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This was so they could be replaced with red-light speed cameras at those two intersections, which began fining motorists in July.

In the last 12 months of operations, the fixed cameras issued $99,002 in fines. In just three months from July the replacement cameras have clocked up a combined $65,489 - or 66 per cent of the revenue from last year.

If the fines continue at this rate, the new cameras could bring in more than twice as much as the old ones by the end of the financial year.

Of the two cameras, the one at Towradgi Road catches more motorists running the red light - 27 in the first three months compared to just 10 at the Railway Street intersection.

Transport for NSW Deputy Secretary for Safety, Environment and Regulation Tara McCarthy said the new cameras were in place to "target high-risk behaviours at the intersections and enforce speeding and red-light running for both north and southbound traffic on Memorial Drive".

There were also crash clusters at those two intersections.

Ms McCarthy said the fines were not expected to continue at the high rate of the first few months.

"There is typically a higher number of infringements in the initial period after a red-light and/or speed camera has been installed at a new location, followed by a rapid and sustained decrease in infringements as drivers modify their behaviour," Ms McCarthy said.

When the fixed cameras were switched on in 2002 they initially issued around 700 infringements per month before quickly dropping to less than 100 a month, which was sustained until the fixed speed cameras were decommissioned this year.