Auckland traffic snarl-up hell: The solutions

City leaders are questioning why it took so long to clear up a harbour bridge crash that caused traffic chaos and brought Auckland motorways to a standstill, leaving drivers frustrated and angry.

Multibillion-dollar roading upgrades, better public transport and a new high-tech computer model could save Aucklanders from the traffic chaos sparked by a harbour bridge crash at the weekend.

Yesterday, city leaders joined motorists - who spent up to four hours on Saturday afternoon stuck in traffic - in demanding to know how a single crash could bring much of Auckland's transport network to its knees.

The midday collision between three motorbikes and a truck, which left three people with serious injuries, closed three of the bridge's four northbound lanes for three hours.

This created a ripple of congestion across the city's streets, roads and motorways as the traffic bottleneck at the bridge dramatically backed up, highlighting the vulnerability of critical Auckland roading infrastructure.

Southbound bridge lanes were also congested because of rubberneckers.

Police have come under fire for their handling of the incident, but experts predict roading projects under way at Waterview and a proposed second harbour crossing would help safeguard against the gridlock experienced by thousands of angry motorists.

Watch: Auckland traffic chaos

Dr Prakash Ranjitkar, a senior lecturer in transportation engineering at Auckland University, said closing three lanes of the bridge would always have a "huge" effect.

The university was helping to develop a probabilistic computer model that would allow authorities to better respond to major disruptions.

Ultimately, the model would predict the behaviour of traffic in response to road closures across large areas, identifying the best points for diversions.

Last night, the NZ Transport Agency (NZTA) said Saturday's ordeal highlighted the need for major planned infrastructure upgrades.

The congestion stretched more than 20km back to Highbrook Drive in Otahuhu, leaving northbound travellers crawling bumper to bumper in the afternoon heat.

Traffic build-up following the incident on the Harbour Bridge. Photo / Jason Dorday

On the Northwestern Motorway, where traffic was already affected by four roadworks sites for construction of the Waterview Connection, traffic was congested to the Lincoln Rd interchange more than 15km away, causing long delays through St Marys Bay and the Central Motorway Junction.

The closure of the Curran St on-ramp also added to the clogging of central city streets, which had earlier been affected by two downtown fire callouts.

NZTA expressed regret for motorists' inconvenience, but said the priority had to be the wellbeing of the injured.

One of the motorcycles involved in the incident. Photo / Victoria Young

However, Auckland Chamber of Commerce chief executive Michael Barnett said it was "totally unacceptable" for a single crash to leave much of the city in gridlock.

While roading improvements might help in the future, the bigger issue was the system's responsiveness to an accident.

"That's an issue the police have to answer," he said.

"I know they have responsibilities in respect of the accident, and assessing and accruing information, but the speed at which they can respond and keep traffic moving, to my mind, is a discussion that needs to be held."

Auckland councillor George Wood, who yesterday wrote to Mayor Len Brown demanding an explanation over the congestion, was more direct in his criticism.

"I was a police officer for 32 years and in my view, they should have been able to clear a scene far quicker than that."

Police were yesterday unavailable to answer questions from the Herald as to why the process took three hours.

A spokeswoman said the serious crash unit was "always mindful of the balance between ensuring a thorough investigation can take place and keeping traffic disruption to a minimum".

Mr Wood said the chaos also pointed to a failure of the wider transport system.

"I think that Auckland Transport and NZTA have got to look really hard at the way they are managing traffic." NZTA state highway manager Brett Gliddon said the crash highlighted the need to develop the $2 billion Western Ring Route as an alternative motorway to State Highway 1's Northern and Southern motorways through the city.

The route - a 47km motorway between Manukau, the top end of the Waitemata Harbour and Albany - would connect the Southwestern and Northwestern Motorways.

"We think diverting traffic along the Northwestern and Southwestern Motorways worked well, but it will be a lot more effective when all those projects are completed and the two motorways connected by early 2017."

Mr Gliddon said the agency would also work with the council, Auckland Transport and the Government on an additional crossing under the Waitemata Harbour.

Labour transport spokesperson Phil Twyford believed Auckland needed a city-wide rapid transit system of trains and buses on top of roading improvements.

Transport commentator Matt Lowrie agreed, noting the northern busway system had seen the number of people catching the bus across the bridge to the city climb from 18 per cent to 40 per cent.

"Where we give people realistic choices, they start to use them."