When you think about it, measuring project success using the Triple Constraint or Iron Triangle is absurd. They measure completely the wrong dimensions

Misleading measures leading to wrong behaviors

Measuring project success by on time and on budget is like measuring a builder’s success by whether or not they exceeded the number of the bricks and concrete they had estimated to be required. Would you say, “Fantastic, no extra bricks required, you’ve done a great job”? I don’t think so.

You’d be looking at the functionality and finish of the house, how it suits your lifestyle needs and delivers the benefits you sought. These dimensions represent ‘success’.

But again, imagine if a builder was being measured in terms of bricks and concrete usage. Then, if you were the builder and you were running out of, say, bricks, you might make some rooms smaller (compromising the result) or leave bigger gaps between bricks (weakening the structure), or make some other compromise to come in ‘on bricks’, as it were.

Changing the measures gives you greater control

But, if as the builder you are being measured on the quality of the result and you’re running out of bricks then you would go back to the owner (sponsor) and give them the options:

1                Buy more bricks – a once off increase in costs

2                Reduce the size of some rooms – an ongoing compromise and future constraint

3                Reduce the quality of the build – an ongoing compromise and reducer of value.

The owner can now make their choice and control the quality and value of the result delivered.

The time and cost-to-deliver estimates are inputs to the project. They are the ‘constraints’ within which the project is to be delivered. However, they are NOT the goal of the project. They are a control framework, an input not an output. They do not define the business value sought.

Topics: Project Success

Further Reading



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Revision History

First published: Simms, J. (Sept 2015) as "The absurdity Of The Triple Constraint Project Success Measures"

Updated: Chapman, A. (March 2020), Revisions and Corrections