It looked like one driver talking to another but as Senior Constable Peter Bines drove past he realised something was amiss.
Yesterday he was formally recognised with a District Commander's Commendation for dedication to duty at the Rotorua police awards.
Mr Bines was off-duty on October 12. He was in his car with his wife Fiona at the Fenton St Amohau St intersection when he saw what looked like one driver talking to another.
As he drove past he saw one man punching the other, he said.
"I was still moving and I think I just put the truck into neutral and got out while it was still rolling and went into work mode," Mr Bines said.