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Many Australian urban dwellers have had their dreams disturbed at some stage by a dull rumbling sensation, barely audible, more felt than heard.
If not something you ate, spousal snoring or nocturnal teeth-gnashing, it’s most likely the tremor of a TBM, or tunnel boring machine.
Our cities are being criss-crossed by these massive mechanical moles, burrowing 24/7 at up to 700 metres a week and turning solid rock into geological Swiss cheese. Sydney, Melbourne, Brisbane, Adelaide and Perth now boast hundreds of kilometres of road and rail tunnels. They’re transforming the way we move and the way we live.
Obvious benefits include improved travel times and reduced surface congestion.
“Major road and rail tunnels compress distance,” said Nicole Bennetts, national head of advocacy for the Planning Institute Australia.
“They effectively bring places closer together, which can unlock redevelopment in underutilised precincts, and make higher-density housing viable where it previously was not.”
Motorway operator Transurban hails tunnel transport as efficient, safe and reliable.
“In the first half of this financial year alone, our customers saved a collective 35 million hours by using our roads,” it said.
Sydney’s NorthConnex (Australia’s deepest tunnel at 90m) has bumped up to 9,000 trucks a day off Pennant Hills Road, significantly improving local noise levels and air quality.
“Independent air quality studies show NOx (nitrogen oxides) concentrations at the roadside are approximately one-third lower,” Transurban added.
It also saves about 20 minutes in morning peak, avoiding 21 sets of traffic lights and theoretically enabling travel from Newcastle to Melbourne without a single stop.
Melbourne’s 6.5km North East Link tunnels aim to take 15,000 trucks a day off local roads and reduce travel times by up to 35 minutes. The West Gate Tunnel, an alternative to the West Gate Bridge, promises to take 9,000 trucks a day off local roads.
Australian motoring bodies generally support tunnel infrastructure.
“We know it comes at a cost,” said NRMA spokesman Peter Khoury, “but our members have told us if the tunnel gets them home to their families quicker, then they’re prepared to pay.”
It’s a similar win for train travel: Sydney’s 24km Metro West project will double rail capacity between Parramatta and the CBD, with fast and frequent services.
There’ll be nine new underground stations. They have already seen a boom in surface redevelopment, including new high-rise apartments, with 10,000 direct and 70,000 indirect jobs created.
The downside is the cost: for example, the Metro West is estimated at $30 billion, courtesy of taxpayers.
“These projects can be expensive,” Bennetts agreed, “so the public value must extend beyond faster commute times.
“The return comes when infrastructure is integrated with strategic land-use planning.”
Road tunnels and surface routes are largely funded by tolls. Melbourne’s CityLink is Australia’s most expensive with car journeys capped at time of writing at $12.38.
Sydney has eight of the nation’s 10 most expensive. The WestConnex M4 is capped for cars at $10.79, the Hills M2 at $10.49.
Those last two are mainly surface roads. Of the tunnels, the NorthConnex is $10.79 for cars, the Cross City Tunnel $7.31.
In Brisbane the Airportlink M7 is $7.16 for cars, Legacy Way $7 and Clem7 tunnel $6.77.
Perth has a 1.6km tunnel on the Graham Farmer Freeway. However, there’s no toll.
It’s not cheap for East Coast drivers, but we’re told most believe the cost is worthwhile.
Transurban’s polling suggests 77 per cent of customers spend less than $10 a week, with tolls only 16th among their top 20 budget concerns.
But the Australian Automobile Association’s 2025 Affordability Index shows a typical household spends an average of $37 a week.
Sydney (“the most tolled city on Earth”) was hardest hit at $60 a week, Brisbane $26 and Melbourne $25.84.
“It’s not an insignificant cost,” said the NRMA’s Khoury. “We know that. But for some families it just works better. And certainly, it works for businesses.”
It’s argued that tolls hurt most in outer suburbs, where drivers have few realistic alternatives to using a motorway.
“Tolls create a clear ‘winners and losers’ dynamic,” said Stewart Bunn, of First National Real Estate.
Bunn also noted that road tunnels can shift congestion, rather than remove it.
There is some relief, in NSW at least. The M5 South- West cashback scheme allows users to claim back the cost of those tolls on a quarterly basis.
And since early 2024 the government has run a $60-a-week toll cap that allows eligible motorists to claim back up to $340 a week spent above that threshold.
As of early 2026, more than $200 million had been refunded. The June NSW Budget reduced the cap to $50, effective for one year from July 6.
The cost will be offset by two-way tolling on the Sydney Harbour Bridge and Tunnel from late 2028.
“This corrects a long-standing inequity,” the government announced. “Tolls on the Bridge and Tunnel are one-way and did not increase once between 2009 and 2023.”
Governments cop criticism whenever tolls go up (often four per cent a year) but say they’re bound by contracts that pre-date their term and extend in some cases until 2060.
NSW said tollway operators deserve a fair return but warns overpriced motorways would be “a handbrake” on productivity and investment.
“We are putting the nail in the coffin of ‘tollmania’ by working on multiple fronts,” NSW transport minister John Graham said. “Tilting the system back in favour of motorists, including the toll cap, scrapping administration fees from mid-year, going digital with communications to drivers.”
That means drivers with unpaid tolls will get an email or text reminder before a final demand arrives in the post.
Transurban has $36 billion invested in Sydney roads. It’s said it supports NSW toll reform and hopes to finalise changes this year.
2026 will also see the appointment of a NSW customer advocate and tollway ombudsman.
Meanwhile the work of the TBMs continues in Sydney, Melbourne, Brisbane and Adelaide (the River Torrens to Darlington, or T2D.)
Other ambitious tunnel projects remain on the backburner.
Sydney’s $10 billion Northern Beaches tunnel was canned in 2023, along with the NSW Blue Mountains tunnel from Blackheath to Little Hartley.
Obstacles include the costs, and environmental concerns.
But traffic bottlenecks on Military Road, the Spit Bridge and the Great Western Highway aren’t going away.
The shortcomings of the GWH are back in focus with its closure after cracks appeared on the 194-year-old “Convict Bridge” at Victoria Pass.
A new bridge is to be built above the old one, but that’s expected to take at least a year.
“We still have unfinished business,” said the NRMA’s Khoury.
§ Sydney tunnels
Sydney boasts one of the world’s most extensive urban road tunnel networks, featuring more than 30km of underground motorways designed to bypass CBD congestion. This network relies heavily on the region’s stable sandstone geology to carve massive routes beneath the city and harbour.
§ Sydney tunnel depths
These underground routes are colossal, with some sections reaching up to 34m wide and 8m high. The iconic Sydney Harbour Tunnel is 2.3km long and sits up to 25m below the harbour floor. It was built using a mix of land boring and eight massive precast concrete units lowered into a dredged trench.
The Longest Tunnel: The WestConnex motorway scheme features twin road tunnels stretching approximately 9km from Kingsgrove to St Peters (the M8), making it one of the longest continuous road tunnels in Australia.
Heavy Excavation: The massive WestConnex M4-M5 Link Tunnels utilised 28 roadheaders simultaneously – the most ever used on a single project in the country. These machines can excavate 1,000 tonnes of rock per day.
Depending on the area, the tunnel’s average depth is about 35m.
The $10.2 billion twin-tunnel provides a continuous toll-road alternative to the West Gate Bridge, running under Yarraville to connect the West Gate Freeway directly to Footscray Road, Dynon Road, and CityLink.
§ Domain Tunnel
Stretches 1.6km long, burrows up to 40m deep beneath the Yarra River, and carries city-bound traffic from the Monash Freeway to the West Gate Freeway.
§ PITFALLS AND ROCK FALLS
The advent of those multi-million dollar, remotely controlled TBMs have made tunnelling a lot safer since the days of picks, shovels and dynamite.
But construction is not without its dangers. One of the more spectacular incidents was Sydney’s M6 tunnel collapse at Rockdale in March 2024.
A 10-metre wide sinkhole appeared in the carpark of an industrial complex, causing the partial collapse of a building.
About a week later, another hole opened about 150 metres away. The collapses were attributed to “adverse ground conditions”.
The site remains waterlogged with broken pipes and machines buried under rubble. But a government wrangle with the contractors appears to have been settled, with work set to re-commence.
In November 2005, a section of Sydney’s Lane Cove Tunnel collapsed during excavation, causing the partial collapse of an apartment building above.
No one was injured, but more than 40 residents had to be evacuated and over 1,000 cubic metres of concrete were needed to stabilise the block.
Two years ago, part of Melbourne’s West Gate Tunnel shut down after a 3am collapse in a cross-passage 25 metres below ground.
Faults sometimes appear long after completion of a tunnel.
Last year, Sydney’s M4 tunnel was closed for repairs to bulging “shotcrete”, or sprayed concrete lining the roof.
§ ARE TUNNELS A GOLD MINE FOR PROPERTY INVESTORS?
By shortening distances and travel times, new road and rail tunnels can offer a rare opportunity for developers and taxpayers alike
You might ask what tunnels have to do with property professionals like conveyancers. A hole in the ground, right?
True… but it’s how they and their associated tollways and rail lines affect housing trends.
By making commuting faster and easier, they open new areas for development and, in older suburbs, redevelopment.
Sydney’s Northwest Metro opened in 2019. It has seen thousands of new units and single dwellings around Bella Vista, Kellyville and Rouse Hill.
Another branch, the 24km underground Metro West, isn’t due to open until 2032. But it has already attracted massive housing investment around the nine new stations. And a blip in property values.
“The pattern is clear,” said Stewart Bunn of First National Real Estate. “When a new Metro station genuinely improves travel times, the market prices in that convenience quickly.”
Research by domain. com.au found houses within 400m of a Metro station sold for almost 17 per cent more than homes further away; units for almost 25 per cent more.
At Five Dock, Deicorp’s $1.8 billion Kings Bay Village, on a former factory site, will deliver 1185 apartments less than a kilometre from the new station.
It’s the first large-scale private project to progress under the Parramatta Road Corridor strategy - a key NSW urban renewal initiative.
Building is underway all along Parramatta Road but much will be driven by the stations at Five Dock, Burwood North, North Strathfield and Olympic Park.
Great if you’re on a Metro line, but what of taxpayers elsewhere? Experts say it’s fair, if new infrastructure boosts housing, productivity and growth generally.
“Not every taxpayer will live near a new station or tunnel,” said the Planning Institute’s Nicole Bennetts.
“But well-planned transport corridors strengthen the wider metropolitan economy by improving access to jobs and enabling more homes where infrastructure already exists.”
We’ve seen that underground rail can cause a property price hike. The hope, however, is that high-density housing near rail hubs will be more affordable.
It’s vital, though, that planning laws allow for the new housing, and that construction keeps pace with infrastructure delivery.
Property analysts say road, as opposed to rail, tunnels tend to produce a more variable response.
“They are not universally popular,” said Stewart Bunn.
“Tolls, portal locations and traffic redistribution mean you can get benefits in one pocket and pushback in another.
“Property markets react at a very local level.”