Doctors say a medical examination will not always pick up conditions that can make driving unsafe for elderly people.
It follows the a case of an 82-year-old woman who crashed her car through six fences in the Canterbury town of Rolleston on Wednesday, after she failed to take a bend.
No-one was injured in the crash.
Drivers over the age of 74 are required to obtain a medical certificate stipulating that they are fit to drive.
The Medical Association's GP Council chairman Dr Mark Peterson says doctors can issue a certificate, subject to a driving test but these can be expensive, and there is often a waiting list.