The model

The toll road concession is a well-understood financial instrument in infrastructure finance. In its standard form, a government body offers a private company the right to build, operate, and toll a road for a defined period — typically 30 to 50 years. The company bids for the concession competitively, agrees a toll schedule and escalation formula, builds the road, operates it, and returns it to the government at the end of the term.

The model has genuine logic. Governments face budget constraints. Private capital can fund infrastructure without immediate public debt. The company takes construction and traffic risk. At the end of the concession, the public gets a paid-off road.

What the model also does — when designed as Australian concession agreements typically are — is transfer a legal monopoly to a private company for multiple decades, guarantee automatic toll increases regardless of traffic or cost conditions, and provide contractual protection against competition. The Morningstar analysis describes this plainly: the ‘wide moat’ that makes Transurban a defensive investment is ‘the government-granted concession that makes each road a legal monopoly.’

WestConnex is the most documented example of how the concession model operates in practice in Australia, because it is the largest infrastructure transaction in Australian history and the level of public scrutiny was higher than for most toll road privatisations.

The public investment inputs are documented. Federal government: A$1.5 billion grant plus A$2 billion concessional loan. NSW Government: A$3.6 billion (A$1.8 billion from Restart NSW infrastructure fund plus A$1.8 billion from Consolidated Fund). The NSW Government also contributed three existing publicly owned motorways — M4, M5 East, M5 Southwest — valued by Credit Suisse at A$9.2 billion. The NSW Government funded additional road works to funnel traffic onto WestConnex tolled sections — including reducing competing lanes on Parramatta Road. And A$5.3 billion of the A$9.26 billion first sale price was reinvested back into completing WestConnex Stage 3.

The Conversation’s analysis estimated that after accounting for all public inputs, the government recovered approximately 34 cents for every public dollar invested. The NSW Treasurer described the sale as a ‘very strong result.’

Infrastructure Australia’s review of the project’s business case was critical of the lack of rigour in appraising alternatives. Modelling showed that simply tolling the existing M4 and M5 motorways would have reduced congestion — without the billions in tunnel construction. That option was not pursued.

Not every toll road concession works as intended. Sydney’s Cross City Tunnel opened in 2005 and entered receivership in 2006 — just one year after opening. The company had overbid for the concession on traffic forecasts that proved wildly optimistic. Sydney’s Lane Cove Tunnel opened in 2007 and entered administration in 2010. Same cause: insufficient traffic, overvalued concession.

In both cases, the concession survived the corporate failure. The roads kept operating, the tolls kept being charged, and the assets were eventually acquired — at distressed prices — by the company with the most to gain from absorbing them into its network: Transurban.

This is the bankruptcy pathway to monopoly. A challenger enters the market with an optimistic traffic model. The model proves wrong. The company goes bankrupt. Transurban — with an existing adjacent network that benefits from the connection — buys the distressed asset at a discount. The concession rights, the toll escalation formula, and the government-guaranteed returns continue. Only the owner changes.

The standard description of the concession model says companies ‘take construction and traffic risk.’ In Australia, this is partially true and partially fictional.

Construction risk is real: companies must complete the road on agreed terms. Traffic risk is more complex. Many Australian concession agreements include provisions that insulate the operator from the worst-case traffic scenarios: minimum revenue guarantees, compensation if competing routes are made more attractive by government, or the kind of arrangement present in WestConnex — where the NSW Government actively reduced competing capacity on Parramatta Road to steer traffic into the tolled tunnels.

The escalation clauses also reduce traffic risk indirectly. If traffic is lower than expected but tolls rise faster than expected — because the CPI or 4 per cent floor is higher — revenue can still grow. The revenue model is partially self-adjusting: lower traffic volume multiplied by higher toll rates can maintain target returns.

Morningstar notes the residual risk: ‘households seeking to save money might use their car less.’ This is the only genuine demand elasticity Transurban faces.

The concession model transfers construction risk to private operators — which is defensible. It also grants a 30 to 50 year legal monopoly on an essential urban road, with automatic toll escalation and various protection mechanisms against competition. The result in Australia: one company now controls most of the toll road network in Sydney, Melbourne and Brisbane, and earns a 75 per cent EBITDA margin.