A reduced 4km/h speed threshold would be strictly enforced through until 6am next Monday, Mr Brown said.
The first fatality was on Thursday at 5.20pm when a 44-year-old female driver from Twizel died on the Fairlie-Tekapo Road in South Canterbury. Speed, the vehicle's poor condition and bad weather were contributing factors, police said.
The driver was not believed to have been wearing a seatbelt.
Shortly afterwards, Alofaifo Afaese, 40, of Helensville, died when the Mitsubishi Pajero in which she was travelling with her husband and two of their children was involved in a collision with a Subaru on State Highway 16 west of Kumeu.
On Friday about 3.15am, Alan Hammond, 80, of Ashburton was struck by a vehicle on the Hinds-Rangitata Highway in South Canterbury. He died as a result of his injuries.
Speed and wet conditions are believed to be factors in a crash that cost an Auckland woman her life about 7.20am Tuesday.
Lysette Michelle Brown, 27, from Whenuapai, was heading north on the Coatesville-Riverhead Highway when her vehicle collided with a truck travelling in the opposite direction. APNZ