The introduction of speeding fines based on the offender's income has been ruled out for this year's South Australian budget, as motorists brace for an expected hike in fees, fines and charges.

Treasurer Rob Lucas has said an increase to speeding fines, vehicle registration and licensing fees was being considered to help offset a budget deficit of $517 million, attributed to a reduction in the state's share of GST revenue.

South Australia already has the highest expiation fees in the country, equalling on average $129 per registered vehicle in 2014-15, according Australia Institute numbers.

By comparison, the next highest state was New South Wales at $75 per registered vehicle in 2014-15; the amount was just $11 in Tasmania.

The SA Council of Social Service (SACOSS) and Uniting Communities have for some time lobbied for a system that would see people on lower incomes fined less for the same offence than those on a higher income, as per European models.

"We were asked prior to the election whether we would commit to it," Mr Lucas said.

"We said we were prepared to have the discussion with them.

"I'm advised it's a pretty complicated process, particularly as people's income levels may or may not truly reveal the extent of their disposable or available income.

"If it's raised every year we'll respond on an annual basis, but it's not going to be introduced in this budget."

Rob Lucas stresses that a decision has not yet been made on fine increases. ( ABC Radio Adelaide: Malcolm Sutton )

Mr Lucas stressed a decision had not yet been made on whether fees, fines and charges would be raised above the standard treasury indexation rate in this year's budget, or by how much, suggesting the GST shortfall could also be filled through "savings to programs and projects".

Motorist fined $290,000

One example of a sliding-scale fine system in action saw a motorist in Switzerland fined $US290,000 for driving his Ferrari 137 kilometres per hour in an 80kph zone in a village near St Gallen in 2010, according to Guinness World Records.

A court assessed the man to be worth $US22.7 million and further increased his fine because he was a repeat offender.

By comparison, people of average or low incomes can receive fines of $US40-120 for lower-range offences in Switzerland.

In its submission to a 2018 select committee on poverty in SA, SACOSS said failing to give way at a roundabout carried a fine equal to 156 per cent of the weekly income of someone on a basic Newstart allowance.

The same fine amounted to about 27 per cent of weekly income for somebody on an average full-time wage.

SACOSS said fines could be "potentially catastrophic, leading to forgoing of food or essential services, or turning to highly expensive pay-day lenders".

"In contrast to this unfair system, Finland has a system of traffic fines based on income," it said.

"The fines are expressed in terms of paying the equivalent of a day's pay rather than a dollar value."

SA Centre for Economic Studies associate professor Michael O'Neil said implementing such a system in Australia would be "very difficult for any state government".

"It does not have access to income tax data to implement this at a state level," he said.

"In any case, speeding at 150kph in a 60kph zone is irresponsible whatever a person's income, full stop."

Confidence in road safety measures is damaged by perceptions of revenue raising. ( ABC South East SA: Kate Hill )

Revenue raising on the roads

Propping up state coffers with excessive fines for even minor speeding offences was introduced by the former Labor government.

It was accused of destroying public perceptions towards road safety measures, while traffic police and speed camera operators earnt the moniker "revenue raisers".

Following public backlash, the former government lowered fines for some offences in 2012 but demerit points were increased and all offences continue to attract a victims-of-crime levy of $60, which doubled from $30 in 2011.

Dr O'Neil said revenue raising through expiation fees had hurt perceptions of road policing, which SA Police "appeared to recognise, as the Queensland Police Association did some time ago".

He said the rising cost of living was already hurting South Australians.

"The lack of growth in employment, underemployment and no real increase in wages is already having an effect, so that while all these fees and charges normally rise each year by CPI, individual wages have not kept pace with the CPI.

"Fees, charges, the cost of water and electricity are biting people's budgets."

Bigger offences could be targeted

Mr Lucas said much of the criticism towards speeding offence revenue in the past had been directed towards excessive fines for lesser offences, such as speeding at less than 10kph over the limit.

"It may well be the Government looks at gradation of this; that is, speeding offences at the more extreme level might be treated differently," he said.

"Don't incur the penalty and you won't have a problem.

"In relation to a fee or charge, if it was to be a massive increase that significantly impacted on take-home disposable income, then that's a fair and valid question at that particular time, but at this stage it's hypothetical."

Opposition treasury spokesman Stephen Mullighan said the Government would be breaking its election commitment to lower living costs if fines, fees and charges were increased above indexation, describing it as the "lazy" option.