"That said, sadly, it's still 42 too many people who have died so far this summer, along with countless others who have been hurt, leaving grieving families and friends behind."
Feedback so far had been largely positive and he warned officers could still ticket anyone doing those speeds.
"We remind motorists that this is no excuse to speed up, and that officers have the discretion to issue notices for anyone travelling faster than the posted speed limit."
Mr Griffiths said the 4km/h threshold remained in force around all schools and police would be focused on targeting speed and drink driving throughout the year.
ACC chief executive Scott Pickering was pleased to see the way most motorists had responded.
"The reality is, the faster you go, the worse your injuries will be. We want to prevent Kiwis from being killed and suffering serious, lifelong injuries on the road."
This week the Automobile Association urged caution when drawing a link between the lower threshold and fewer deaths.
"Over the last two months we have seen a massive road safety advertising campaign and a major police presence on the roads," it said.
"Whether the reduced tolerance would be as effective without this publicity is a question the evaluation will need to look at."