We aim to develop a new model for the success of megaprojects. Megaprojects are often said to fail because they finish late and/or overspent. But megaprojects are usually complex, so small changes in input can lead to disproportionate changes in output. So the time and cost targets at the start can have little validity. They are useful targets, not values which can be used to judge success or failure. We suggest a megaprojects is a success if it produces a worthwhile result at a time and cost that makes it valuable.
We develop a new model for the success of megaprojects, and asses its applicability against a number of case studies from well known sources.
We identify four dimensions of megaproject success: they produce an output at a time and cost that makes it valuable; they achieve the desired outcome and benefit at a time and cost that make them valuable; they deliver positive net present value; they deliver a business or public need at a time and cost which makes it valuable.
We propose a new model for megaproject success that moves away from the so-called iron triangle or triple constraint, which are meaningless in the context of complex projects. Time and cost to completion cannot be predicted on complex projects. However, targets are required because a megaproject must produce a valuable outcome at a time and cost that makes it valuable.
The paper produces a new way of assessing the success of megaprojects which will lead to a larger number of megaprojects being assessed to be successful. It indicates what is truly important, that the megaproject should produce and outcome of value at a time and cost that makes it valuable.
Megaprojects often produce benefits to society over and above the financial benefits. Often an economic benefit cannot be paced on these social benefits, which makes it problematic to assess the value of the project. In one of our cases economic value was placed on the social benefits, and the benefit:cost ratio was increased from 0.85 to 2.5.