South Australia's borders are now effectively in lockdown as the state battles to contain the spread of coronavirus.

Key points: A huge queue has formed at the SA-WA border as drivers seek to get home

A huge queue has formed at the SA-WA border as drivers seek to get home Any non-essential travellers entering SA will now have to commit to self-isolation

Any non-essential travellers entering SA will now have to commit to self-isolation Exemptions will apply for a range of categories, but the intention is to limit the spread

It comes as authorities confirm another jump in the number of SA cases, which currently stands at 170 — up by 36 from the same time yesterday.

Huge traffic queues have formed on the Nullarbor at one of 12 crossings established around the state's borders, following both SA and WA enacting border restrictions simultaneously.

A line of cars and other vehicles stretched for more than a kilometre as people desperately sought to get home ahead of the restrictions coming into effect at 4:00pm ACDT.

South Australia is one of several states and territories to have implemented stringent restrictions on cross-border travel.

The SA Government announced the "unprecedented action" on Sunday on the recommendation of chief public health officer Nicola Spurrier.

What does the border closure mean?

A police officer speaks with a driver at an SA border checkpoint at Pinnaroo. ( ABC News: Michael Clements )

The move has been widely described as a "border closure", but travel will still be permitted, albeit under very strict conditions.

The intent is to limit all non-essential travel between states.

On Sunday, the SA Government declared a "major emergency" and has established a dozen checkpoints where travellers will be stopped and required to sign a declaration about their health and ability to undertake mandatory self-isolation for two weeks.

The main restriction will be a 14-day isolation requirement, meaning anyone deemed to be a non-essential traveller will have to commit to self-quarantine, regardless of whether they are displaying symptoms.

"This is no longer something that is optional. It is mandatory. It is the social responsibility of everyone in this state to make sure they are abiding by these rules," Premier Steven Marshall said on Sunday.

"What we have seen in recent days is an increasing number of people who have contracted the virus from people visiting from interstate, or South Australians who have been interstate returning to South Australia.

"This has forced our decision to close our borders in South Australia."

Drivers queued at the WA border on the Nullarbor before the self-isolation rule comes into effect. ( ABC News: Rhiannon Stevens )

SA Police Commissioner Grant Stevens said fines of up to $20,000 for individuals and $75,000 for corporations would apply to anyone found to be illegally bypassing the checkpoints.

"There's no way of physically stopping every person entering South Australia without investing significant resources to that effect, so we are targeting the major arterial routes into South Australia including by road [and] rail," he said.

"We're expecting that people will voluntarily comply with this direction."

How's it going to work?

South Australia shares borders with five other jurisdictions — WA, the Northern Territory, Queensland, New South Wales and Victoria — which is the most of any state or territory in Australia.

A total of 12 border checkpoints have been established to limit the flow of traffic between jurisdictions.

All non-essential traffic entering SA will now have to commit to self-isolation. ( Supplied )

SA is not the only state to have declared a border lockdown — Tasmania was the first, before WA, Queensland and the Northern Territory all followed suit.

According to police, travellers heading into the state will be required to provide certain information.

"Names and details will be recorded, including their South Australian address for the period of self-quarantine," police said.

Commissioner Stevens said the checkpoints had been established under the Emergency Management Act and would be operational 24/7.

"Police officers will be approaching vehicles as they come through the checkpoint and speaking to the occupants of the vehicle, obtaining their details and providing them with a notification in relation to their obligations," he said.

"[They're required to] go straight to an address they nominate where they can self-quarantine for 14 days. No other person is able to enter that residence unless they live there or for emergency reasons.

"They'll have to rely on friends, family or other support if they rely on goods or services during that quarantine."



How has it been so far?

The border between WA and SA has been swamped with people trying to make it home before the restrictions began.

Emma Pegrum and her boyfriend Tom Van Beem decided to return to WA ahead of the lockdown, only weeks after they had moved to Sydney to start a new life.

Tom Van Beem and Emma Pegrum lined up in their car at the WA-SA border. ( Supplied )

Ms Pegrum said cars were backed up for a kilometre to get into WA.

"We got here at 12:40pm SA time and are about 30 cars deep," she said.

The pair left Sydney at 4:00am on Monday, about a day-and-a-half before WA's borders were set to close.

"We had a 15-minute conversation, rang family as well and then pretty much made the call on the spot and started packing our bags and packing the car," Ms Pegrum said.

"Figuring out what time we actually had to cross the border and at what time we'd have to leave each day to make sure we made it in time were some serious mathematical problems.

"It's a pretty weird time, crazy decision-making for everyone."

ABC reporter Lucy Robinson has been driving in the opposite direction, leaving Port Lincoln on South Australia's Eyre Peninsula to head to Toowoomba in Queensland before its border closes.

ABC reporter Lucy Robinson is among the many travellers. ( ABC News: Lucy Robinson )

"I left Port Lincoln on Monday afternoon, which was much earlier than I'd planned, I was going to leave on Saturday morning," she said.

She said when she heard the Queensland border would be closing at midnight on Wednesday, the decision to leave was made very quickly.

"I had a whole week of goodbyes planned and ended up having to pack up in a couple of hours, and not say goodbye," she said.

"At the moment I'm in Broken Hill, hoping to spend the night in Wilcannia, before heading to Queensland via Bourke, to hopefully get across the border before midnight.

"It is quite a strange feeling because it feels like the information is changing quite fast."

Who is exempt?

The SA Government has said exemptions to the new restrictions will apply for what it labels "essential transport".

That includes the transport of health and medical supplies, health personnel and patients, food and commercial supply chains, health workers, travel of a relative or caregiver of a dependant person and emergency services.

Air travel has come to a virtual standstill, with only a few travellers in an otherwise deserted Adelaide Airport. ( ABC News: Brittany Evins )

Fly-in, fly-out workers in the mining industry or national level sporting teams could also be exempt but only if they had "approved disease control mechanisms in place".

"Farmers and other primary producers who have properties that extend beyond borders or are in close proximity to borders will be exempt, and they will find it quite easy to access those exemptions," Commissioner Stevens said.

SA Police said the following categories could be eligible for exemptions because they fall under the umbrella of "essential travel":

National and state security and governance workers

National and state security and governance workers Health services

Health services Essential medical treatment

Essential medical treatment Transport and freight services

Transport and freight services Skills critical to maintaining key industries or businesses

Skills critical to maintaining key industries or businesses Emergency service workers

Emergency service workers Cross-border community members

Cross-border community members People passing through en route to other states

People passing through en route to other states Compassionate grounds