Traffic out of Auckland and Wellington is beginning to build up, with police warning motorists heading away for the long weekend to take extra care.
The NZ Transport Agency (NZTA) said traffic was already starting to get heavy on Auckland's Southern Motorway, with the stretch between Manukau and Takanini particularly congested.
A crash on the Harbour Bridge blocked one of the northbound lanes about 3.30pm, although the crash has now been cleared.
In Wellington, NZTA said traffic heading northbound along the Kapiti Coast was heavy, and congestion was expected in that area until this evening.
A crash involving two cars near Masterton about 3.20pm closed both lanes of SH2, but the road has now reopened.
Both lanes were closed between Opaki Bridge and Loop Line and diversions were in place.
One person was in a serious condition after the crash.
NZTA has released a hot-spot map for the entire country, showing when and where the heaviest flows of traffic are expected over Labour weekend. It can be found here.
Police in the western Bay of Plenty said they expected high traffic volumes on Friday and Saturday as visitors made their way to Mount Maunganui and Tauranga, especially on State Highway 29 over the Kaimais and State Highway 2 from Waihi to Tauranga City.
Senior Sergeant Ian Campion, from Western Bay of Plenty Road Policing, said police would be out in force.
"Motorists should expect delays and allow plenty of time for travel to their destination.
"Police will be focusing on excessive speed, checking that everyone is wearing their seatbelt or restraint correctly and drivers are not using mobile phones.
"If you are involved in a crash, regardless of the cause, speed is the single factor that most affects the outcome.
"It's the difference between serious injury and death, being maimed for life or walking away."
Last year's road toll: five dead, 21 seriously injured
Labour Day Weekend officially starts at 4pm today and ends at 6am on Tuesday.
Last year, five people died and 21 people were seriously injured in crashes on New Zealand roads during the long weekend.
Police will be enforcing a reduced speed threshold of 4km/h over the long weekend.
More than 250 people have died on the roads so far this year - 71 of whom were not wearing seatbelts, even though they increased the chance of surviving a crash by up to 50 percent.
Assistant Commissioner of Road Policing Dave Cliff said fine margins could make all the difference when travelling at speed.
"We really ask people to make sure that they, their passengers, their children, their babies, are safely restrained inside the car so if something goes wrong, they're infinitely safer if they have got their safety belt."
Meanwhile, Māori whānau travelling to remote parts of the country have also been warned to take care on the roads this long weekend.
Whānganui police iwi liaison officer Katrina Moore said Māori families often travelled to major family events in tribal areas over Labour Weekend, and that put them at higher risk of road accidents.
"We take that opportunity to go home and reconnect and rejuvenate with our whānau. And particularly on Labour Weekend, far too many of our people are dying.
"Stay awake, stay alert, and just take any actions to reduce that risk on the road, so responsible driving, driving to the conditions, all those sorts of things."