This is even after we account for the whopping $56 billion investment over the next 30 years that is likely to come from central and local government.
The gap is partly the result of historic underinvestment in public transport, but also because of our rapidly growing population.
Auckland's population is projected to grow by around one million by 2030, with 60 per cent coming from within New Zealand. We are growing nearly 50 per cent faster than New Zealand as a whole.
That's an average of nearly 3000 more Aucklanders every month moving around our city. A growing pressure on our roads, bus services, trains and ferries.
What revenue sources we use to fill that gap will be the most important debate Auckland is going to have during the remainder of this decade. Also important is how we manage the pressure on our roads. International experience shows that more motorways alone tend to lead to a corresponding increase in traffic. Public transport alternatives, however, can significantly relieve the pressure.
Last year, an influential group of transport, business and community stakeholders, the Auckland Consensus Building Group, put forward two broad options for tackling this challenge - the result of nine months of careful analysis and consultation with Aucklanders.
One option was to increase rates, fuel taxes and fares, along with higher government contributions and tolls to fund major new roads. The other was the introduction of road pricing, supplemented by much smaller increases in all of the above.
Put simply, we were told that based on the evidence, we could have higher rates and fuel taxes for all Aucklanders, or look seriously at the option of road pricing.
Few dispute that a failure to do either would inflict serious damage to Auckland's economic potential, environment and liveability.
A future of traffic congestion is not the future Aucklanders want.
This month, the consensus building group has reformed to work up these two options in detail, so the council can make fully informed decisions early next year as part of the Long-Term Plan review. Their work will enable us to present Aucklanders with detailed and credible options for meeting the funding gap, which we will consult on publicly next year.
This is unique. Rather than asking the Government to pick up the bill, we are asking them to let us pay our share, and to determine how we do it.
There is a strong case for the Government to make a significant contribution towards the funding.
Auckland accounts for around 38 per cent of New Zealand's GDP and 60 per cent of population growth. New Zealand needs Auckland as its economic powerhouse. To achieve that, we must invest in world-class infrastructure, including a modern and integrated transport system.
But it is not realistic to expect the Government to meet all of the shortfall.
We want central government to work with us, and we will need their support to implement the option Aucklanders support us taking forward. But fundamentally this is about working towards an Auckland solution to an Auckland problem.
Len Brown is Mayor of Auckland.