A fairer demerit point system for NSW drivers has been unveiled but it will not start until September - 10 months after the state government flagged the changes.

Roads Minister Michael Daley first announced an overhaul of the current system in November last year, and on Monday released the details.

Under the new system, a driver travelling up to 10km/h over the speed limit will lose just one demerit point and be fined $81.

Anyone caught doing between 11km/h and 20km/h over the limit will lose three points and be fined $189, while those detected between 21km/h and 30km/h will lose four demerits and have to pay $324.

Previously, anyone caught speeding between 0 and 30km/h over the speed limit lost three points, but the fines varied for different speeds.

Mr Daley said the new system was fairer for drivers, but necessary updates to various agencies' computer systems, including the Roads and Traffic Authority (RTA), meant they would not take effect for another six months.

"We're putting some balance back in the demerit point scheme," he told reporters.

"Motorists asked for me to treat them more fairly at the bottom end of the scale and that's exactly what I'm doing."

Despite being six months away, Mr Daley said the changes would not be retrospective.

The new offence levels will retain the three-month suspension and $621 fine for anyone caught travelling between 31km/h and 45km/h over the limit, but they will now lose five points instead of four.

Those detected travelling at 45km/h or more will still lose six points and their licence for six months.

The NSW opposition welcomed the changes, but said it should not take so long to implement them.

"It shouldn't take six months to get this package up and running," Opposition Leader Barry O'Farrell told reporters.

"The reality is there will be drivers out there who will be caught by a system that the government now accepts is unfair."

Motoring group NRMA said the new demerit point system was more sensible, saying it was never fair someone doing 1km/h over the limit lost as many points as someone travelling at far greater speed.

NRMA president Wendy Machin said she would have liked to have seen the changes introduced more quickly, but making the laws retrospective would be riddled with problems.