What is the most common cause of big projects over running on their estimated budget? For example, I recently learned that the HS2 train line in the UK will be nearly £75bn over the estimated budget! How was the estimate so wrong?

Question

What is the most common cause of big projects over running on their estimated budget? For example, I recently learned that the HS2 train line in the UK will be nearly £75bn over the estimated budget! How was the estimate so wrong?

In: Engineering

Answer 1

[https://en.wikipedia.org/wiki/Hofstadter%27s_law](https://en.wikipedia.org/wiki/Hofstadter%27s_law)

>” Hofstadter’s Law: It always takes longer than you expect, even when you take into account Hofstadter’s Law. “