Why do construction projects always seem to go over budget?

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Why Construction Projects Always Go Over Budget

From pre-construction costs to inflation to unexpected site conditions, there are a lot of reasons construction budgets rarely align with construction costs. Let's talk about it!

Video talks about the OPCC value, a heavily-qualified initial estimate. Numbers generally have an uncertainty range associated with them, cultural practice is not to report that currently.

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A piece by The Age previously. Look at the transport spend vs other VIC government portfolio areas 

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Shiny infrastructure projects and the not-so-shiny cost-benefit analyses - podcast

Is it worth it? It's the question that should be asked whenever governments come up with a shiny new infrastructure idea. But too often, major projects are announced as election promises, without evaluating the cost and the value of the project to taxpayers.

Some insight into the operation of IA.

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Oct 20, 2015
Follies of Infrastructure
Why the worst structures get built, and how to avoid it
Bent Flyvbjerg

At 19:30 min into the video, the negative information bias appears. In an interview with a planner, they submit that they know the true cost of the project but passing that up to their superiors is difficult because it is inconvenient for their superiors to listen to.

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Why do so many infrastructure projects have cost blowouts? | 7.30

Some of the nation's biggest construction and transport projects are running tens of billions of dollars over budget. Why do so many of these large projects seem to follow the same pattern, over promising on costs? Adam Harvey reports.

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Snowy Hydro 2.0 Project

Pitched Cost: $2.0 billion
Expected Actual Cost: $12 billion
Blowout Factor: 6x

Experts say the expectations for Snowy 2.0 were wildly optimistic from the beginning, with Turnbull announcing it just two weeks after it was first proposed by Paul Broad, the former chief executive of the publicly owned Snowy Hydro corporation.

https://www.brisbanetimes.com.au/politics/federal/florence-the-2400-tonne-machine-that-came-to-symbolise-snowy-2-0-s-woes-20230901-p5e17w.html

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Interesting potential explanation (possibly partial) for why QLD projects especially Priority A ROW seem to cost a lot more than in WA.

Would need further investigation.

[ozbob]

The Guardian --> 'The cheap option'?: why the Gold Coast may be on track to build the most expensive light rail in the world

Limiting reliance on the private sector, hiring foreign experts, and improving contracting transparency could be ways to keep costs down, experts say

Light rail is as much a fixture of the Gold Coast as bikinis or boogie boards; the attractive yellow vehicles trundling up and down the coast suit the place so well it feels as if they've been there much longer than their decade in service.

As in Queensland's second city, light rail has sprung up in Canberra, the Sydney CBD, Parramatta and Adelaide. Similar "trackless trams" are soon opening in Perth and Brisbane. One of the only places there aren't plans is Melbourne, home to the world's largest tram network. Around the country, there has been a proclaimed renaissance in light rail.

On opening in 2014, the Gold Coast light rail was an immediate success. Public transport patronage jumped by 32% in the first three years, even before stage two opened in 2017. At the 2018 Commonwealth Games, the G:link zipped 100,000 passengers a day around the glitter strip in its distinctive yellow carriages. ...

Some good points raised in this article.  View at The Guardian.