A brawl broke out on Auckland's Southern Motorway after a driver took exception to the way another motorist was changing lanes, police say.
Emergency services were called to the incident on the Market Rd off-ramp at 1.06pm, a police spokeswoman said.
"A vehicle had come in to join the motorway. A vehicle in another lane has taken exception for some unknown reason and the vehicles have pulled to the side and a person has been assaulted."
It did not appear there had been any contact between the vehicles.
It was unclear at this stage how many people were involved in the brawl. Police investigations are ongoing.