A flight through one of two 2.4km tunnels on Auckland's Waterview Connection shows how far the development has come.

Extraordinary video footage has shown how the massive Waterview Connection motorway development in Auckland is slowly taking shape.

New Zealand's largest and most ambitious roading project is on track to be finished in early 2017 when it will complete the Western Ring Route around the city at last.

Half of it is underground. Alice, the purpose-built tunnel boring machine, has already created one of the twin 2.4 kilometre tunnels required and is well into her work on the second.

She started building the first one from Owairaka to Waterview in November 2013, breaking through into daylight at Waterview on September 29 last year.

She was then turned around, and is now on her journey back southwards and due to come out at Owairaka this spring.

The Waterview Connection involves construction of 4.8 kilometres of six-lane highway to connect State Highway 16 in the west with State Highway 20 in the south.

It will be a badly needed alternative to the Southern and Northern motorways along State Highway One through the central city.

It involves major upgrades on SH16, the Northwestern motorway.

The causeway over the Waitemata Harbour between Waterview and Te Atatu is being raised and widened, including a bus shoulder lane city-bound.

The improved Lincoln Road interchange is largely complete, and the Te Atatu interchange and St Lukes Road bridge are also being significantly upgraded.

The project will provide new amenities for the communities it passes through, such as a major revamp of the Waterview Reserve next to the Great North Road interchange and a new cycleway from Owairaka to Waterview.