The "Good Samaritans" then put themselves between the couple and phoned police, Mr Friend said.
While this was happening, the victim walked off and her attacker followed.
The two women jumped back in their car and went after them, where they found the man kicking his partner's head while she lay on the ground, Friend said.
They intervened again, making sure the woman was safe until police arrived.
The man was arrested and taken to Hamilton police station where he was charged with male assaults female.
"There is no doubt in my mind or of the officers involved in this incident that the actions of these two women prevented the victim from suffering serious injury, and in accordance with this we are looking at the most suitable way we can recognise their bravery in ensuring such a violent offender was stopped," said Mr Friend.
On average, 14 women, six men and 10 children are killed each year by a family member.
"Nationwide our staff get called to about 200 domestic violence incidents each day and it's only through members of the public stepping up to the mark, like these two women did, that the message domestic violence is not ok will get through."
- nzherald.co.nz