Auckland's rapid population growth is increasing traffic chaos on the city's roads with a dire prediction that one in three main roads will be congested by 2020.

A quarter of the city's busiest roads, including Lake Rd, Lincoln Rd and routes to the airport, are already clogged during the morning and evening peaks, up from 18 per cent three years ago.

Motorway speeds have fallen from 64km/h to 55km/h at peak hours between 2014 and 2016 and the morning crawl on the Southern Motorway from Papakura to the city has dragged out from 46 to 67 minutes in just three years.

The rapid pace and scale of Auckland's population growth - the city grew by 121,000 people, the size of Tauranga, in the past three years - is behind the figures, provided to the Weekend Herald by Auckland Transport and the New Zealand Transport Agency (NZTA).


Assuming the rate of growth continues, Auckland Transport said about a third of the city's main roads will be congested by about 2020.

Every week, 800 new vehicles are registered in Auckland, further challenging the city's geography of a narrow isthmus where all the land available for roads and public transport has been developed, says NZTA Auckland highway manager Brett Gliddon.

"That's forced existing transport corridors to absorb more and more traffic," he said.

Bumper-to-bumper traffic, overcrowded buses and trains and long journeys to the airport are a daily nuisance and a reminder of a city under pressure from decades of under-investment in infrastructure.

The city's housing crisis has pushed the price of an average home to $1 million and Aucklanders have been reminded about the vulnerability of the water system with images of diluted sewage pouring into the harbour and weeks of shorter showers following the extreme storms last month.

Auckland's growing pains are felt most strongly on the roads, where huge gains in public transport - rail boardings increased by 19.4 per cent in the past year to 19 million boardings - cannot compete with the number of new cars on the roads. Vehicles travelled 13.4 billion kilometres on Auckland roads in 2015, up 1.2b from 12.2b kilometres in 2012.

In an Auckland Transport board paper, manager Hamish Bunn says the rate of growth in public transport boardings is well ahead of population growth, but it has not dented the growth in private vehicle travel leading to a marked increase in peak-hour congestion across arterial roads, particularly over the past two years.

National Road Carriers boss David Aitken says truckies are quitting out of sheer frustration at sitting idle in traffic.


Aitken said about 10 years ago trucks could do five trips a day across the city. That was now down to two or three trips today. He blamed under-investment in infrastructure going back to the 1960s and Auckland Council's Unitary Plan for increasing housing and industry without a parallel plan for infrastructure.

Gliddon said Auckland's recent unprecedented growth had translated into 44,000 more vehicles on the roads than this time last year and a 5.7 per cent increase in motorway trips between 2015 and 2016.

He said the $1.4b Waterview tunnel would complete the motorway link from the west to the south and provide a second route through Auckland, creating greater reliability and resilience.

"While it's not designed to remove congestion altogether, the western ring route will provide a better balance of traffic flows across the entire road network, including helping to remove cars from local roads," Gliddon said.

Extra lanes opened on the northwestern motorway in the past year had led to significantly quicker journeys in peak hours. It now took an average of 20 minutes to travel between Nelson St and Westgate during the evening peak, compared to 26 minutes in 2012, Gliddon said.

He said extra lanes on the southern motorway between Manukau and Papakura would be completed next year, ease the existing bottlenecks and lead to more consistent journey times.


Labour's Auckland Issues spokesman Phil Twyford said the party would be launching a massive programme of investment in Auckland transport infrastructure for September's general election.

The programme would focus on rapid transit, including rail, light rail and buses, as opposed to National's focus on motorways, Twyford said.

Labour has pledged $680 million to pay half of a $1.36b costs for the first stage of a light rail system from Wynyard Quarter to Mt Roskill. It also wants to build a northwestern busway and cut back immigration to give the city a breather.