A serious crash near Whangārei has seen part of State Highway 1 shut down, adding more than 30 minutes to holidaymakers' travel times.
Two people are critically injured after two cars crashed near Puhipuhi Rd, Whakapara, around 5.50pm.
Part of State Highway 1 has been closed as a result and heavy traffic is already building.
Motorists should stay away from the area if they can, police warn.
A detour suggested by the New Zealand Transport Agency, travelling through Jordan Valley Rd instead, is estimated to add 30 to 40 minutes to people's travel times.
Traffic on the roads tonight has already been heavy as Auckland, Waikato and Bay of Plenty residents head away for the long weekend.
NZTA had previously estimated northbound traffic from Whangārei would be at its busiest between 2pm and 6pm.
It's expected the section of State Highway 1 will remain closed for some time.