"The offender is reported to have driven the victim to the motorway end of Main North Rd where he turned into Dickeys Rd and parked in an enclosed logging yard approximately 300 metres from the intersection."
The woman was sexually assaulted in the car for some time, before she was dropped off at Main North Rd near Johns Rd.
She is being supported by Canterbury police and Victim Support.
The offender is described as Maori, aged between 30 and 40, clean shaven and wearing a white t-shirt and 'Dickey' brand shorts that came to below the knee.
He was driving a dirty white early model Mazda Familia four-door sedan with tinted rear lights. It was clean and tidy inside.
Police want to hear from anyone with information about the man or vehicle described, or any other information on the inquiry.
Phone Canterbury police on 03 363 7400, or anonymously contact Crimestoppers on 0800 555 111 or at www.crimestoppers-nz.org.