"Police officers have the discretion to stop and ticket people driving at any speed over the limit every day of the year."
Speed was often the difference between a close call or an agonising stay in hospital, he said.
It was up to officers to decide whether to issue tickets for drivers caught driving only a small amount above the limit.
The enforcement threshold for speed cameras during summer will stay at 4km/h.
Zero tolerance will remain in place until it is reviewed by police.
Today also marks the beginning of stricter alcohol limits. The limit for drivers over 20 years drops from 400mcg of alcohol per litre of breath to 250 mcg.
For drivers under 20, the limit remains at zero.
Adult drivers blowing between 251 to 400 mcg of alcohol per litre of breath will not face court action but will receive a $200 infringement fine and 50 demerit points on their licence.
Those over 400mcg will face criminal court charges, as they have done until now.
Police advice is to avoid drinking altogether before driving, or arrange a sober driver or other alternative transport.