Earlier this month, the auditor general released his damning report on Sydney’s WestConnex tollroad, concluding that its $3.5bn of federal funding and loans did not provide taxpayers with value for money. But WestConnex is an even worse deal for suburban motorists, who will be expected to pay much of the $17bn cost − for what is essentially an inner-city road freight scheme, designed to increase truck productivity between Sydney’s port and industrial areas.

In the past, private tollroads have been funded through a combination of tolls and taxpayer subsidy. But the unprecedented cost of WestConnex means the NSW government also needs to toll publicly owned motorways that are currently free.

A toll of $8 a day will be introduced on the M4 this year, and a toll of $14 a day will be introduced on the M5 East in 2020. In addition, the M5 West toll will be extended beyond 2026 − when it had been due to end – meaning the whole M5 is set to cost $27 a day, with no cashback. Suburban motorists will be paying for WestConnex for decades, even if they never use it.

If this tollroad is such a bad deal for both taxpayers and motorists, then whom exactly will it benefit?

A major beneficiary will be the road freight industry, because the new tolls will clear traffic from truck routes. After tolling begins on the M5 East in 2020, it will carry less traffic than it does today. Proponents of WestConnex claim it will take trucks off suburban streets. However, by increasing the competitive advantage of road freight over rail, it will actually encourage more trucks onto the road network. During peak times, truck operators will pay to use the tollroads. However, they are likely to avoid the tolls at other times, meaning more trucks on suburban streets off-peak, and at night.

Another beneficiary will be the future corporate owner. For a fire-sale price, it will get an asset with above-inflation toll increases guaranteed until 2060. Tollroad king Transurban’s share price has skyrocketed in recent years, no doubt partly in anticipation of adding WestConnex, the M4 and the M5 to its Sydney toll road monopoly.

The state economy will benefit, in the short-term at least. Spending $17bn on any infrastructure, useful or not, will usually stimulate the economy. However, there’s no clear evidence urban motorway expansion helps long-term economic growth in a city like Sydney, which already has an extensive, high-capacity road network.

On the contrary, it encourages inefficient urban sprawl, and there are few on-going jobs – even toll collection is automated now. That $17bn would be better spent on much-needed public transport, which would have long-term economic and social benefits, as well as creating jobs.

For commuters and tradespeople, the new tolls will clear traffic from existing motorways, and the new tunnels will bypass traffic signals. Those who can afford the tolls should be able to drive into the inner-city faster than today, but will emerge into a traffic jam. For those unable to pay, driving times will increase significantly. Rail will remain the fastest option for many trips.

However, very few commuters will get to enjoy the shorter driving times facilitated by the new tolls. A three-lane motorway can handle maybe 14,000 commuters in the morning peak. That’s just 0.4% of Sydney’s working age population. In contrast, a single railway can transport 10 times as many into the heart of a city, at a much lower cost.

WestConnex is being marketed to the public as a “congestion buster”, though any congestion relief will be mostly down to the new tolls, and is unlikely to last. Other, untolled roads will become more congested, due to toll-avoidance and induced demand. In particular, traffic on Parramatta Road, which is being narrowed to four lanes, is expected to worsen significantly.

Overseas governments have accepted that congestion is a fact of modern city life; that there can never be enough road space to allow everyone to drive into their city centres – private cars simply need too much space, and building more roads only encourages more traffic. Even Los Angeles is now investing in fast and efficient public transport.

Given the choice, most suburban commuters would prefer a swift, comfortable rail service that takes them straight into the heart of the city, than to be charged $27 each day to drive through a dark monotonous tunnel, inhaling truck fumes. With more commuters switching to public transport, space could be freed up on the road network for those who need to drive.

It’s becoming increasingly clear that WestConnex is a bad deal for Australian taxpayers, and a bad deal for Sydney commuters. But it’s not too late to correct course. Construction on stage two has barely started, while the $7bn stage three is still unfunded.