Police said speed at both ends of the spectrum remained a problem, with slow drivers adding to the holiday frustrations by congesting the roads, while speedsters were putting everyone at risk by driving above the speed limit.
Waikato district commander superintendent Bruce Bird said it was important for people to drive to the conditions.
"We ask people to drive in a considerate manner, check your mirrors and where safe, pull over and allow other motorists to pass."
Waikato senior sergeant Steve Ambler said it was important motorists drove at a speed that would allow them to react quickly if needed.
"Our message here is we want everyone to watch their speed this summer and drive to survive," he said. "While the weather is fine, increased numbers of vehicles on the road means drivers need more patience."
As well as the serious bus crash at Otira Gorge, near Arthur's Pass, that's led to the closure of State Highway 73 between the gorge and the pass, there was also heavy traffic on State Highway 1 between Warkworth and Wellsford.
The agency tweeted motorists should "expect delays and consider using an alternative route".
Other potential hotspots were being signalled on the agency's Summer Journeys planner around SH2 near Maramarua east of the SH1 interchange, SH2 between Paeroa and Tauranga and SH6 between Cromwell and Queenstown.
Some traffic was also expected around some of the bigger New Year's Eve celebrations, such as Rhythm and Vines in Gisborne.
But senior sergeant Dan Foley at the Eastern District Command Centre said police were well prepared to cope with the increased numbers on the roads.
He said people seemed to be behaving themselves at this stage, with only a few minor crashes reported.
"We've got extra staff keeping an eye on things ... Gisborne is a working operation ... all is well planned."
