Rozelle Interchange soon to open 24 kilometres of underground tunnels to Sydney drivers

It's one of the most complicated underground interchanges ever built – and in the next week or so, 100,000 Sydney drivers will begin navigating it as part of their daily commute.

The Rozelle Interchange consists of 24 kilometres of tunnels twisting around each other deep below ground.

It funnels cars in and out of a dozen different entrances and exits that connect the City West Link, the Iron Cove Bridge, the Anzac Bridge and the M4-M8 Link between St Peters and Haberfield.

By 2028, it will also link up to the planned Western Harbour Tunnel.

But drivers are being assured that navigating the route will be as simple as following the signs, and they'll only need to decide between two choices at any point.


How does ours stack up against the world's wildest?

There are plenty of other spaghetti junctions around the world that would probably beat the Rozelle Interchange for the title of the world's wackiest.

The High Five Interchange in Dallas, Texas is a five-level stack interchange rising as tall as a 12-storey building — it includes a mind-blowing 43 bridges.

The Hi-Five interchange where LBJ Freeway and Hwy 75 connect is shown with vehicles on a snowy and icy road

The Hi-Five interchange where LBJ Freeway and Hwy 75 connect.(AP: Tony Gutierrez)

China has more than its fair share of spectacularly complex interchanges — from the six-level Puxi Viaduct in Shanghai, to the swirling circular Nanpu Bridge interchange in the same city.

Aerial image of Puxi Viaduct in Shanghai withy network of roads coming together buildings and gardens in between The six-level Puxi Viaduct in Shanghai.(Wikimedia Commons: Alex Needham[1])A complicated highway network with several roads feeling into large circular road, green gardens in the middle The Nanpu Bridge interchange in Shanghai.(Wikimedia Commons: Yhz1221[2])

And there's the original interchange which coined the name "spaghetti junction", the Gravelly Hill interchange in the UK city of Birmingham that was built in 1972.

'Spaghetti Junction' Gravelly Hill Interchange in Birmingham, United Kingdom at night with network of roads lit up This "spaghetti junction" interchange in Birmingham was built in 1962.(Flickr: West Midlands Police[3])

But the snarl of tunnels that make up the Rozelle Interchange might just be the most complex one ever built underground, according to Transport NSW deputy secretary Camilla Drover.

"We're not aware of an underground interchange that connects three motorways," she said.

"We've got three layers of tunnels to deliver the interchange and it will also eventually go over the Metro West tunnel as well.

"So that's four layers of tunnelling with total tunnel depths between 35 metres and 65 metres deep … that's as deep as a 20-storey building."

Camilla Drover, wearing a builder's helmet while stood in a park

Transport NSW Deputy Secretary Camilla Drover said sections of the tunnel system are 20 storeys deep. (ABC News: Sarah Gerathy)

How was it built?

About two-thirds of the tunnels will carry cars, while the rest were built to house ventilation and electrical equipment.

Six and a half million tonnes of rock and soil had to be excavated from deep underneath the houses and streets of Rozelle in order to dig the tunnels.

Some 1.74 million metres of electrical cabling, 7,400 lights and 132 jet fans had to be to be installed.

And 308,000 square metres of road pavement were laid.

In total, about 20,000 construction workers have been involved in the project since building began four years ago.

Steve Keyser standing in a park wearing high vis

Rozelle Interchange project director Steve Keyser said logistics has been a challenge.(ABC News: Sarah Gerathy)

Project director Steve Keyser said it's taken a huge amount of logistics to get all the workers and equipment in and out of the tunnels each day.

"We peaked at probably about six or seven hundred workers at once, working 24/7 underground, 23 road headers," he said.

"Bringing that all together seamlessly has been a great challenge."

Even with a global pandemic thrown into the mix, the project has kept on track to open as scheduled.

So, was it all smooth sailing?

In a nutshell, no.

The interchange has created plenty of controversy during its lifetime.

The state government's initial proposal looked very different, with planners envisioning large surface ramps crisscrossing each other.

The decision to push the interchange underground has allowed 10 hectares of parkland, which is scheduled to open in December, to be constructed above it on land reclaimed from the old Rozelle railyards.

An aerial photograph showing Sydney city with the Rozelle highway development in the centre.

There was some public backlash throughout the project's planning and construction.(Supplied: John Holland CPB)

But the construction process has been long and messy, with homes being compulsorily acquired and some residents complaining of unbearable noise as tunnel boring machines drilled beneath their homes around the clock.

Plenty have objected to the three 35m exhaust stacks above the park, as well as a 235m road bridge linking The Crescent in Annandale to Victoria Road and the Anzac Bridge.

It's also been disruptive for drivers, who have been forced to navigate about 40 different traffic changes during construction.

How do I navigate this thing?

Despite its complexity, drivers are being assured by Transport NSW coordinator-general Howard Collins that navigating the interchange will be pretty simple.

"In reality, for most people, you will have two choices on which route you take … from a motorist's point of view, it's either keep to the left or keep to the right."

He said all turns were clearly signposted, with plenty of warning.

And if drivers want a dress rehearsal, there is a series of animated previews of their route online[4] that will take them through the drive, turn by turn.


So far, there's been no mention of a toll amnesty similar to that which has been in place when other motorways first opened.

But if you take a wrong turn, Mr Collins said the one thing you shouldn't do is stop — even if it means you'll have to retrace your route and pay the toll again.

"For the sake of a few dollars, you don't want to cause some major traffic jam or something even worse," he said.

Mr Collins is confident that if there is a pile-up, or fire in the tunnel, its ventilation and monitoring systems are well-equipped to handle it.

"We have the latest technology, over 800 cameras, we've got crews on stand-by literally ready to go if there's any incidents in the tunnels," he said.

Will I get home faster?

The interchange is expected to slash travel times for drivers, particularly in the afternoon and evening peak as drivers head out of the CBD to the city's west and south.

The interchange is the final piece in the WestConnex motorway's promise to deliver a 20-minute saving on travel time between the CBD and Parramatta.

The interchange's only free section – a 1.1km tunnel under Victoria Road at Rozelle — will bypass seven sets of traffic lights on a road that is notoriously banked back.


But authorities are warning traffic will get worse before it gets better, as drivers adjust.

Roads Minister John Graham recently told a budget estimates hearing that the adjustment could take up to six months.

But Mr Collins is more optimistic.

"The first couple of weeks generally is when you do tend to get a little bit more slowing down as people actually maybe are even admiring some of the infrastructure," he said.

"But we are then heading for school holidays, when we see a 10 to 15 per cent reduction in traffic."


  1. ^ Alex Needham (
  2. ^ Yhz1221 (
  3. ^ West Midlands Police (
  4. ^ series of animated previews of their route online (