Here's my favourite example of this. NYC recently opened the first stage of the Second Avenue Subway. This is a project that was initially started ~90 years ag

Here's my favourite example of this. NYC recently opened the first stage of the Second Avenue Subway. This is a project that was initially started ~90 years ago and has been started and stopped multiple times in the intervening years. I believe the final version used none of the original tunnels however. It cost ~$6B for 1.5 miles of track [1]. The budget was padded at probably every level (eg [2]). There are a bunch of other contributing factors. Now compare Crossrail [3]. This is a hugely ambitious project to build some 117km of track and 21km of tunnels under London in an east-west direction connecting Kent, Essex, Heathrow, central London and the Thames Valley. This was in the planning stage in the early 2000s (possibly earlier) and construction commenced in 2009 or so. It is near completion, only 2-3 years behind the original schedule (that I recall from 2003 at least) with cost overruns of around 20% (IIRC) coming out to ~17B pounds. The UK and US are similarly developed industrialized nations. NYC and London are large cities with all the problems that entails. Actually, London is far worse because it's been for literally thousands of years, including some ~500 years of Roman occupation. The scale of Crossrail (adjusted for cost) compared to the Second Avenue Subway is unreal. It's basically an order of magnitude. The reasons for this are complex. There's no single determining factor. There is failure all the way from the Federal through the state and local governments as well as with the companies that build these things, the oversight of those projects, how the bids are awarded and the people who are actually doing the work. This should at least convince you that there is a problem and it's absolutely massive. [1]: https://en.wikipedia.org/wiki/Second_Avenue_Subway https://en.wikipedia.org/wiki/Second_Avenue_Subway [2]: https://jalopnik.com/heres-the-most-damning-report-yet-on-why-the-new-york-c-1821651731 https://jalopnik.com/heres-the-most-damning-report-yet-on-wh... [3]: https://en.wikipedia.org/wiki/Crossrail https://en.wikipedia.org/wiki/Crossrail