Red zones will be eliminated from 6pm AEDT on Friday, with the area of Cumberland downgraded from red to the only remaining orange zone.

According to Victoria's traffic-light system of travel restrictions, anyone travelling from Cumberland will have to self-isolate and get tested within 72 hours of arrival, remaining in isolation until they get a negative result.

All other parts of NSW will be designated green, which only requires travellers to get tested if they become symptomatic.

Premier Daniel Andrews said people travelling from the Cumberland area should still get tested.

"We're extremely happy to see the last red zone in NSW be downgraded," he said.

Victoria closed its borders to NSW on New Year's Day after virus outbreaks in Sydney, causing traffic chaos on state borders as holiday makers rushed home.

Victoria has now reached 23 days with no new local coronavirus cases, and 27 cases confined to hotel quarantine including one new case on Friday.

But the state of emergency has been extended for another month, to February 26.

Fragments of the virus have been detected in wastewater in three Victorian towns in recent days.

The remnants were detected in Gisborne on Tuesday, Hamilton on Wednesday, and Leongatha on January 19.

The Department of Health said the results were unexpected, because there were no confirmed cases in these communities at the time.

The government is urging anyone who lives in or has visited Gisborne from January 24 to 26, Hamilton from January 25 to 27 or Leongatha from January 17 to 19, to get tested if they have any symptoms.

There are 95 wastewater sites being tested at least weekly for viral fragments.

Meanwhile, the easing of border restrictions will mean Victoria Police can start scaling back their duties on the NSW border.

Several hundred Victoria police have been on border duty, leading to debate about whether they are being spread too thinly, and Thursday's Bourke Street driver incident heightened those concerns.

But Police Minister Lisa Neville and Assistant Commissioner Luke Cornelius said police numbers in the Melbourne CBD had been unaffected, also noting the incident was sparked by a number plate check.

"I'm very happy that our standing footprint to cover the city is sufficient," Mr Cornelius said.

Ms Neville said more than 800 police were involved in hotel quarantine and that would increase to more than 1000.

Also on Friday, Ms Neville was unapologetic about some Australian Open personnel having to wait more than 14 days to be freed from hotel quarantine.

Players and support staff started leaving quarantine on Thursday night, with the last expected out by midday on Sunday.

Australian Associated Press