Cheney Suthers Lawyers director solicitor Dannielle Ford said the new penalties would include on-the-spot $561 fines and automatic three-month driving suspensions.

"This means that a person who has been driving for 20 or more years, with minimal traffic record and no other criminal history, may lose their licence on the spot for registering a reading of 0.05 - 0.079," Ms Ford said.

"In some circumstances, the difference between a low-range reading and being under the legal limit may be a difference of 10 or 15 minutes or a few mouthfuls of alcohol."

Ms Ford said people could appeal and the courts could overturn the suspension by way of a Conditional Release Order with or without conviction but the first court date was typically four to six weeks after the offence.

"In this time, a person may be unable to work, care for sick relatives or do school pick-up and drop-off."

Ms Ford said many people also didn't understand what a standard drink was.

Aboriginal Legal Service acting chief executive officer Janelle Clarke said she was concerned the new laws would impact Aboriginal people living in areas where public transport was not reliable or non-existent.

"Getting to work, taking children to school and attending medical appointments are just some of the factors that may lead a court to consider that a disqualification is not necessary," she said.

"ALS accepts that the laws must apply to all but we are outraged that this step has been taken largely due to a perception that magistrates are not applying their discretion appropriately.

"As we know, a high proportion of Aboriginal people are in jail as a result of driving offences and those incarceration rates could rise under these new laws."

However, Campbell Paton and Taylor partner and solicitor Mason Manwaring said if a driver paid the penalty notice, the change seemed to be an efficient way of dealing with low-range PCA matters and he hoped the suspension would act as "a significant deterrent to offending".

"It seems to me there is opportunity for a significant saving of police time and resources, court time and money with the proposed new regime, and I see it as a positive regime, provided drivers have the opportunity of being heard in court if they so wish," Mr Manwaring said.

"I suspect that there will be about 50 per cent or more of drivers who will elect to have their matters heard in court and I do not expect the delay to be any more than currently experienced."