Kendal Briquel Levine, 20, who remains in a critical but stable condition at Canberra Hospital, was trapped under her car after it was hit while she was attempting to get in.

A Monash man came to Levine's aid, with ACT Policing suggesting he may have saved her life.

The man used a trolley jack to lift the damaged car, free the woman and place her in a recovery position before ACT Ambulance officers then came to her aid.

"By stepping in and assisting, there's little doubt this man helped reduce the trauma on the woman," Acting Superintendent Traffic Operations Rod Anderson said.

It is understood Levine remains in a coma and her parents, who live in Hawaii, made an urgent trip to Australia to be by their daughter's bedside.

The 20-year-old is from Hauula in Hawaii and was in the country serving in the Australia Sydney South Mission for the Church of Jesus Christ of Latter-day Saints and had received a full scholarship to an American college before coming to Australia.

"Sister Levine remains in critical condition and is receiving excellent medical care. Our thoughts and prayers are with Sister Levine, her family and her companion during this difficult time," a spokeswoman from the Church of Jesus Christ of Latter-day Saints said.

The spokeswoman said all mormons in Canberra, Goulbourn, Cooma and Merimbula had been invited to fast for the young woman.

ACT Policing is calling for witnesses to help wth the investigation.

Around 4.30pm on Friday, Levine had been returning to her vehicle, a Toyota Corolla, which was parked on the nature strip some metres from the roadway, and had opened her driver's door to re-enter the car.

A white Chrysler 300C, driven by a 26-year-old Monash man, has collided with the driver's side of the Corolla

Anyone who may have seen the collision and who has not yet provided a statement to police is urged to do so by contacting Crime Stoppers on 1800 333 000, or via act.crimestoppers.com.au.