SYDNEY - The New South Wales police commissioner says it's not realistic to stop police car pursuits altogether, after a chase in Canberra ended in the deaths of a family of three and a disqualified driver.

NSW police say they stopped chasing 23-year-old Justin Williams, who was driving a stolen Mazda 626, just before he ran a red light and hit a vehicle at the corner of the Monaro Highway and Canberra Ave in Canberra early on Sunday.

Heading in the other direction was a 33-year-old Canberra man, a 29-year-old woman and their 4-month-old boy.

The couple and their baby were killed instantly when the Mazda 626 slammed into their car.

Williams died later in hospital.

His 18-year-old girlfriend, who was in the passenger seat, was taken to Canberra Hospital in a critical condition.

The Daily Telegraph in Sydney reported that 10 months ago Williams woke from a coma after crashing a stolen car on May 14. He was unlicensed at the time.

NSW Police Commissioner Andrew Scipione told ABC Radio: "It's important that we let the coroner get access to these officers and to all of the facts. Then the coroner can make an educated decision and hand down his findings for all of us to see."

Scipione said there had been a reduction in the number of pursuits in the past few years. But he did not believe it was realistic to ban them outright.

"Of course that has got to be balanced with this notion that you cannot let necessarily anyone go out there and think, 'well, if I just go a little bit faster I'll get into a pursuit, police are going to drop off and therefore I've got immunity almost from being arrested or from somebody trying to stop me committing a crime'."

Scipione said it was important to assure the community that police were trying hard to stamp out crime. The public wants "us to go out there and be strong and be courageous and do the job that we are paid to do."

- AAP