Vehicle numbers are up by nearly 10 per cent on Tauranga's roads and the traffic surge is causing problems for Bay emergency services.
Firefighters and ambulance staff are struggling to attend incidents quickly and police are having to deal with a spike in crashes caused by driver frustration.
The latest figures from the NZ Transport Agency show that Tauranga traffic volumes grew by 9.7 per cent in the year to September, with the Bay of Plenty region up 8.4 per cent.
Tauranga's increase was more than twice the national average of 4.8 per cent.
Most commuters in the region are familiar with growing traffic congestion, but the problem can have serious consequences for emergency services.
The officer in charge of road policing in the Western Bay, Senior Sergeant Ian Campion, said he was seeing an average of 25 accidents a week, compared with about 17 a year ago.
"We've certainly noticed an increase in driver frustration and non-compliance with road rules," he said. "It's high time for people to adjust their driving, to put aside another 10 minutes to get where they're going."
Tauranga senior firefighter Derryn Davidson said staff had definitely noticed more vehicles on the roads during the past year, and fewer people were pulling to the left to allow fire trucks past.
"Obviously that can prevent us from getting to incidents as fast as we would like," he said.
A St John Ambulance worker in Tauranga, who would not be named, said rush-hour traffic made life more difficult around Turret Rd, 15th Avenue and Pyes Pa.
"Anything that delays our time to treatment potentially puts people at risk."
Tauranga residents depend on their vehicles more than people in most other parts of New Zealand, with 97 per cent of journeys taken by private car. They also have the lowest usage of public transport, cycling and walking.
City Mayor Greg Brownless said the worst snarl-ups were at intersections, but fixing those would only be a short-term solution.
"It will just snarl up again in future," he said. "We need to see what we can do with public transport systems."
Tauranga councillor Rick Curach, who chairs the council's new transport committee, said city residents were wedded to their vehicles and there needed to be a "modal shift" towards other forms of transportation.
"The battle is to get people out of their cars," he said.
Priority One strategic projects manager Greg Simmonds said planning had been "pretty good" and infrastructure had been built in advance to tackle the traffic increase.
"Certainly [travel] takes us slightly longer than we're used to, but we're not getting comments that it's hindering productivity.
The Bay of Plenty Times earlier reported that city traffic was up by an annual rate of 8 per cent to 9.5 per cent for various months this year, but the rate has increased since then.