"While things are looking good at the moment, we expect those travel times and volumes to build as the day progresses."
The spokeswoman said leaving Auckland sooner, rather than later, might be a good option.
"This will be a busy day on the highways. People should allow plenty of time for their journey so they don't get impatient. When they get impatient that's when they make bad decisions. Plan well and allow plenty of time for your journey."
In Hamilton, bargain hunters heading to The Base mall are advised to expect delays.Police Senior Sergeant Andrew Townsend said traffic was "crawling" along Wairere Drive and Te Rapa Rd.
"There have been three non-injury motor vehicle crashes on Wairere Drive since 9am, including a seven-car non injury crash. Police request all drivers to not be distracted and be patient if you are travelling to the Boxing Day sales," he said.
The first signs of holiday traffic heating up are emerging on the Waikato Expressway.
The transport agency has just issued the following advice to motorists: "Expect significant delays southbound on the Waikato Expressway at Pokeno for traffic turning left on to SH2."
In Wellington, traffic is building on State Highway One at the Mana Esplanade, a 50 kmh pressure point north of the city.