Major traffic jams on State Highway 2 in Wellington caused travellers to miss flights, disrupted court trials and delayed rubbish collections in the capital.
A car crashed and a truck broke down within minutes of each other about 6.30am, both near Horokiwi.
The car was quickly removed but it took about four hours for the truck to be cleared.
At one stage the queues stretched back to Melling and the backlog wasn't cleared until after 11am.
The traffic woes led to delays in the capital's courts.
Many people called for jury service were caught up in the backlog, as were Corrections staff coming into the city from Upper Hutt, meaning trials could not start as scheduled at 10am.
Rubbish and recycling trucks were also caught up in the traffic problems and Wellington City Council said collections would be two hours late.
Wellington Airport had advised people to allow extra time to get to their flights.
A spokesperson said people ended up missing flights because of the congestion.