A Fire and Emergency NZ spokesman said emergency services were called to the scene of the crash about 1km past the Sign of the Kiwi Cafe on the Governors Bay side at 1.20pm.
The car came to a stop more than 100m down the hillside.
The FENZ spokesman said firefighters pulled one person out of the car and a helicopter transported them to Christchurch Hospital.
An ambulance was also at the scene, along with two fire engines, police and the helicopter.
A St John spokeswoman said the person was seriously injured.
Dyers Pass Rd is closed with cordons set up at Summit Rd and Governors Bay Rd.
The FENZ spokesman said there were no guard rails where the car left the road. In March. it was announced about 3km of guardrails, costing $7.25 million, will be added along Dyers Pass Rd over the next 18 months to improve safety.
The crash follows the death of Anthony John Deverson, 78, who was driving along Summit Rd near Evans Pass Rd last week. His car went off a bank and no other vehicle was involved.
And in November last year, 17-year-old Tayla Alexander and her 15-year-old sister Sunmara died in a crash on Summit Rd.
