Hamilton police are investigating an incident of road rage in the city which saw a man taken to hospital.

The man, who worked for Go Bus, was in a company van on Boundary Rd bridge on Thursday morning when another driver got out of his car and started throwing "heavy" punches at him, a witness told the Waikato Times.

Go Bus director Craig Worth said the attack was "quite savage".

The driver was taken to Waikato Hospital.

He had been wearing the company uniform and was enroute to swap with another Go Bus driver when the attack happened.