Traffic is heavy around the North Island as people flock back home on Auckland Anniversary Day with crashes in both the Waikato and Northland only exaggerating the already slow crawl.

Motorists are being urged to avoid SH16 near Mangakura after a fatal crash involving a car and two motorcycles near the Kaipara Harbour closed the road. A detour remains in place and the road is not expected to reopen until at least 8.30pm.

Further north, SH1 near Whakapara has reopened after a motorcyclist died in a crash involving a four-wheel-drive on Russel Rd just before 5pm. Police remain at the scene.

In the Waikato, traffic is heavy along SH2 heading west towards Paeroa and the NZTA is urging people to expect delays and, if possible, put off their journey.

Advertisement

Earlier a two-car crash on the northbound section of SH1 between Huntly and Taupiri at 2.24pm also caused delays to both north and south-bound motorists.

Waikato police senior sergeant Phil Ruddell said initial reports indicated there were no serious injuries, but police, the Fire Service and St John were in attendance.

"While the crash is not serious there will be delays in traffic. We are asking people to be patient. We understand everyone wants to get home and we are working to clear the scene and the backlog as quickly as we can," Ruddell said.

Police are also advising drivers to exercise caution and keep a good following distance.

The New Zealand Transport Agency earlier warned of "heavy congestion" for traffic leaving the Whitianga region, heading south on SH25 and urging people to delay their journey.

It has made for a slow trip for those heading through Tairua - many on route to Auckland or back to Tauranga. Congestion was finally easing about 5pm.

The NZTA's hot spot predicter showed the westbound lane of SH2 at Maramarua was expected to be "heaviest" from 11.30am to 7pm.

Further north, it also showed traffic between Puhoi and Wellsford on SH1 would be heaviest between 10.30am and 7pm in the southbound lane.

Advertisement

The southbound lanes on SH1 in Whangarei and Kawakawa were also expected to be busy today.

In both places this was expected to last from 10.30am to 3.30pm.