Documents obtained by The Daily Telegraph show the 25 new school zone cameras installed since July have been catching motorists at a frantic rate, issuing 158,551 fines worth $20.7 million in the second half of the year.

Several of the cameras, part of 50 promised in the aftermath of an accident involving Sophie Delezio, have already become the busiest in NSW.

Among the new locations, the twin cameras operating in each direction at the Hume Highway, Bankstown, have issued fines worth $4.57 million in six months, nabbing 33,802 motorists.

At King Georges Rd, Beverly Hills, twin cameras issued 41,429 tickets worth $5.481 million. Another new camera, on the Pacific Highway at Lindfield, has snapped 15,337 motorists for fines totalling $1.922 million.

The high number of infringements from the new cameras is astonishing as all are in school zones with flashing warning lights in operation during the 40km/h periods.

The RTA also placed variable speed message signs before commissioning the new cameras and for the first few weeks afterwards.

Another initiative is that all motorists caught in the first 30 days get a warning notice rather than a fine.

"As the cameras become more established the RTA hopes to see a decline in the number of repeat offenders speeding through these zones," an RTA spokesman said.

The new school zone cameras pushed the total number of fines issued by fixed speed cameras in 2007 to 620,194, with a face value of $70,904,543. This is double the $34,234,396 from 350,665 fines issued in 2006.

And there is more pain ahead for speeding motorists, with the RTA planning 11 more cameras in school zones this year.

The RTA denies Treasury will benefit from the revenue, saying all monies go towards funding the cost of the cameras and school zone improvements.

"Money generated from school zone infringements is returned to school zone safety," the spokesman said.

Pedestrian safety campaigner Harold Scruby said no one should "bleat" about revenue raising as school zone speeders deserved heavy fines.

Mr Scruby called on Roads Minister Eric Roozendaal to go ahead with plans to use 25 mobile speed cameras in other school zones.