THOUSANDS of drivers are being fined for speeding just a few kilometres above the limit, smashing the myth a margin of error is allowed on NSW roads.

More than half the 13,000 drivers caught by roadside mobile speed vans in NSW were travelling between 1km/h and 10km/h above the limit, data shows.



The RTA appears to be ignoring a so-called "common law discretion", most likely because the former state government forced operator vans to be clearly marked with orange and white stripes and signage, instead of being undercover.



The move resulted in a likely push by the RTA to collect fines at the lowest speed band possible.



Office of State Revenue data shows 7341, or 56 per cent of all drivers caught speeding in the first year of the mobile operation were in the "10km/h or under" band.



In comparison, just 13 per cent of all speeding fines issued by police in 2010/11 were in the same speeding band, indicating they are using some discretion.



With the RTA preparing a report into the effectiveness of the mobile operation for the government, the data shows a total of 13,129 drivers were fined $2.02 million in the 12 months to August 31, 2011.



The RTA's mobile speed camera contract obtained by The Daily Telegraph states there is an allowance for some discretion to be given to drivers.

But the margin of tolerance levels are so secret employees must sign a confidentiality agreement and are banned from writing about them in correspondence.



"Enforcement threshold speed is the speed of vehicles at which RTA initiate prosecution after exercising their common law discretion by allowing a margin or tolerance above the posted speed limit," according to the RTA's Scope of Service document dated October 2010.



"Any enforcement thresholds to be applied on mobile speed camera systems shall be in accordance with RTA and must be approved before implementation. Threshold information shall not be written in correspondence, emailed or transferred without written permission of the RTA."



Read more about the tougher RTA at The Daily Telegraph