Chief Health Officer Kerryn Coleman and Chief Police Officer Neil Gaughan made the call on Monday afternoon, but said the random checks weren't the same as a full border closure.

"ACT Policing will be conducting random interceptions to speak with drivers about the new public health directions and any requirements to quarantine in the ACT," Dr Coleman and Deputy Commissioner Gaughan said in a statement.

"This will not be a permanent measure and will supplement ACT Policing's compliance activities."

Cars travelling into the ACT from NSW weren't being stopped by police and checked on Monday, but it's expected a police vehicle will be stationed on the Highway from Monday night.

While there is no permit process to cross the borders, any ACT resident returning from COVID-affected areas in NSW must complete an online application form and complete 14 days quarantine.

Questions over resources and the power to make the call appeared to delay the decision to man the border, with the decision made against attempting to man the dozens of border crossings between NSW and the ACT.

The ACT recorded no new cases of COVID-19 on Monday, with just one case in the territory in hotel quarantine.

Dr Kerryn Coleman said ACT residents should re-consider their need to travel in NSW in coming days and be prepared for the requirements to change as more information comes to hand.

She also said Canberrans should be prepared for the current restrictions on travellers from Sydney, the Central Coast and Wollongong to still be in place on Christmas Day, but a final decision would be made in coming days.

At the press conference earlier on Monday, Deputy Chief of Police Michael Chew said there was planning around border strategies in March and April but resourcing those strategies was an issue.

"We're not at a stage where we will be checking every vehicle or every person that comes back into Canberra through the roads," he said.

"We're looking at some presence on the Federal Highway to capture traffic coming down the highway that would predominantly be from Sydney."

Dr Coleman said she didn't want to rely on police enforcement to make sure people did the right thing and followed the public health orders.

Earlier on Monday, Dr Coleman said on ABC radio she expected the police to have some kind of presence on the Federal Highway.

"We have a great tradition in the ACT, over the past nine months people have really come along with us, people's compliance to date and coming on board with all of our measures has been fantastic," she said.

"So while we are looking at this option to try and support and strengthen that, and ensure we protect residents, we are really relying on people to do the right thing."

Acting Health Minister Chris Steel said the government wasn't considering asking for support from the defence force to help patrol the border at this time.

"We're asking people to use common sense," Mr Steel said when asked if the government was taking a risk by relying on people to do the right thing ahead of long-planned family celebrations.

On Monday, NSW Health confirmed another 15 cases connected to the Avalon outbreak, and Dr Coleman said ACT residents who had been in Sydney need to pay attention to the constantly updated list of exposure sites.

A huge volume of road traffic was reported on the Hume Highway heading south into the ACT throughout Sunday as the pandemic numbers out of Sydney began to climb.

Concerns exist internally within ACT police that should the current NSW outbreak escalate further and spread and that road travel restrictions be required, the operational workforce required to set up those roadblock checkpoints would be a massive drain on resources.

ACT Policing are already part of the team checking on people in home quarantine, and the more than 100 government officials in hotel quarantine.

One senior ACT police officer, who did not wish to be identified, said that 24-hour ID checks on the border with NSW would be an "enforcement nightmare".

Previously flagged back in March-April when the docking of the Ruby Princess cruise ship in Sydney Harbour and the resulting COVID-19 outbreak sent a massive wave of infection throughout NSW and beyond, the prospect of a border roadblock would have a massive disruptive effect for regular travellers from areas such Queanbeyan, Murrumbateman, Googong and other nearby NSW regional areas.

There are understood to be around 70 road entry points from NSW into the ACT, including four major highways, the Federal Highway, Kings Highway/Canberra Ave; Monaro Highway and the Barton Highway, and nine secondary roads.

Epidemiologist at Australian National University Peter Collignon said it was reasonable for the ACT government to take a more measured approach to the border with NSW as the cases so far were sufficiently tracked.

"At the moment it appears to be a cluster in the Northern Beaches, there's not really any unidentified or mystery cases," Professor Collignon said.

"Most people who will get infected should already be in isolation or quarantine," he said, pointing out it was unlikely there was high numbers of people in Sydney with undiagnosed infections.

Even when Sydney experienced the outbreak related to the Crossroads Hotel in July, the ACT didn't get cases of community transmission, even though that cluster had around 200 cases.

"Obviously if there's transmission in a city or region you do have to restrict movement in those areas, and into other areas, until you're aware of what's going on. But the major risk where there is uncontrolled infection numbers and a lot of mystery cases, like we saw in Melbourne, it was quite different in Adelaide, and so far in Sydney, but we will have to see what's happening in the next few days."

Professor Collignon pointed out the ACT has harsher restrictions now than in winter, a riskier time and when there were more cases.

"It's appropriate to restrict travel but that's different to hard border barriers when the data isn't all in, you should really only do it when there's mystery cases circulating."

Australia's success so far at suppressing the virus meant the tolerance by the population and governments for even small outbreaks had gone down, Professor Collignon said, but also people were becoming too relaxed and acting as they would before the pandemic without social distancing or hygiene measures.

Professor Collignon said it was important for people to try and have their Christmas celebrations outside, instead of inside with air conditioning.

"If you can have a BBQ outside that is safer than inside with an air-conditioned hot dinner."

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