The Drug Foundation says driving while under the influence of drugs is now a serious safety problem in New Zealand.
A survey by the foundation has found a quarter of those surveyed admit taking cannabis before driving.
The survey suggests more than half of the 1200 respondents thought it was alright to drive after taking cannabis and 16% claimed it actually improves their driving.
It also found the more a person uses a particular drug, the more likely they are to believe it is alright to drive while under its influence.
From December this year, police will have the power to conduct compulsory roadside tests on drivers who they suspect have taken drugs.