There will be "good news" for public transport in Tuesday's State Budget, SA Transport Minister Stephan Knoll has said, despite some stakeholders fearing a reduction in services.

Mr Knoll admitted there was an "existing saving task, and we'll need to deal with that", but pointed out the cutback had been revealed in last year's budget.

"We aren't going to see any decreases in train or tram frequency and we've already done what we were going to do to the buses," he said.

"In fact, there's good news when it comes to public transport in the budget."

Transport Minister Stephan Knoll has been shaking up Adelaide's public transport. ( ABC News: Nick Harmsen )

Mr Knoll did not reveal what the good news was but said another extension of the O-Bahn, this time to Golden Grove, was on the Government's public transport agenda, along with more Park'n'Ride services.

On Saturday he announced $8 million would be committed in the budget towards a replacement of the Tonsley train station — to be closed as part of the Flinders Link project — although consultation on its exact location will continue.

There was also some hope for those wanting more trams in Adelaide, namely a city tram loop and a potential extension to O'Connell Street in North Adelaide.

City loop on the radar

Ahead of losing Government last year, the Labor Party installed an East End tramline as a precursor to a city loop or an extension to Norwood.

It also installed a short and near-pointless spur north up King William Road in a less than subtle move to encourage further investment.

"There are 10 projects that we said we would be undertaking a business case development into, and one of those was a city tram loop," Mr Knoll said.

"In fact, we'll have a little bit more to say about that, not as part of the budget, but as something else we're doing in the next couple of weeks," he said.

But Mr Knoll said a wider network proposed for Greater Adelaide, including extending the tram to Norwood, or lines to Prospect and up Unley Road, would not be happening on his watch.

"When we look at making future investments in public transport, we need to look into the future," he said.

"I don't think in five to 10 years time we're going to be building light rail networks.

"There is a whole host of new technology that is coming down the pipe very quickly and whether that be electric buses, some sort of autonomous version, hydrogen buses, as well as trackless trams, it's going to provide better solutions for public transport."

An O-Bahn extension into Adelaide's CBD via tunnel opened in late 2017. ( ABC News: Tom Fedorowytsch )

Feeder network priority

The Government in last year's budget planned savings of up to $15 million by rationalising low patronised bus services, reducing duplication and optimising timetables.

In May, Mr Knoll announced the planned cessation of bus contracts by June 30 — a date later extended to the second quarter of 2020 — and put out tenders for new bus services to direct people onto city-bound trains and trams in a "feeder" service.

He also announced a $1 million trial for Uber-style, bus-on-demand services in low-patronage areas — a move Opposition transport spokesperson Tom Koutsantonis said at the time would help the Government cut a planned "$46 million" from the budget.

People for Public Transport president Josephine Buckhorn is nervously awaiting the budget. ( ABC Radio Adelaide: Malcolm Sutton )

People for Public Transport (PPT) president Josephine Buckhorn was concerned some services were going to be cancelled because "on paper they look like they're not frequently used".

She wanted the Transport Minister to meet with stakeholders and organisations like the PPT before making decisions about existing routes.

"Given a prediction they're going to be cutting, from what I understand, around $40 million from public transport, we are certainly worried about what's going to happen," Ms Buckhorn said.

"I understand they need to cut the budget but I think they need to exercise more caution because the impact of cutting a service and have it disappear can be disastrous.

"It's extremely difficult to reinstate."

Ms Buckhorn said the on-demand trial should run alongside other options, such as utilising smaller buses.

Mr Knoll said that as part of the bus tender process currently underway, he had asked companies to suggest ideas for better feeder technology, believing such integration was "key" to increasing patronage across the network.

Support for connecting services

Doctor Sekhar Somenahalli, from the University of South Australia's School of Natural and Built Environments, agreed that interchanges played a vital role in urban public transport systems.

Sydney's has also being trailing on-demand bus services. ( Flickr: Simon_sees )

He said connecting them with a "high-quality and high-frequency" service should be priority.

"As per our recent study, a significant number, 40 per cent, of respondents surveyed were willing to use public transport at interchanges if they were well connected by shuttles," Dr Somenahalli said.

He said figures from his own research found a "spatial mismatch" between the bus feeder network and the location of Park'n'Ride users at the Paradise bus interchange.

"Only 37 per cent are within 400 metres, walkable areas, of the existing bus feeder service," Dr Somenahalli said.

"This highlights the need for improving the feeder coverage appropriately to reduce the car parking demand at the interchanges.

"Here an on-demand bus system could be trialled."

Doctor Somenahalli believed investment in a tram network should be a top priority as well, along with extending the O-Bahn, and giving buses priority on roads while supporting city cycling and walking networks.

Adelaide's O-Bahn could be extended to Golden Grove. ( ABC News: Malcolm Sutton )

Recouping costs with fare changes

The 2018 budget also forecast reduced public transport fares, but Mr Knoll has since abolished two-section tickets on trains and trams from July 1.

This means people travelling small distances on a single ticket will have to pay a full fare of $5.50 instead of $3.50, or $2 instead of $3.70 if they are using a tap-on metrocard.

Mr Knoll, however, maintains frequent users will only be marginally worse off — about $150 a year — if they purchase 14-day or 28-day passes, suggesting that a very small fraction of people bought two-section passes.

Two-section passes will be abolished on trains and trams from July 1. ( ABC News: Chris Lawless )

"It's a tough call; we don't shy away from that," he said.

"For those people who are regular public transport users, it shouldn't be a huge increase.

"If you're a casual public transport user, then by definition it will only affect you for those times you use it."

The 2018-2019 State Budget will be handed down on Tuesday.