Why “the iron triangle” (of project management) isn’t

Over and over, people quote the iron triangle of project management – relating verbatim to the elements time, scope and cost from the wikipedia article or by the slightly less formal adage “Cheap, Fast, Good – pick any two”.

Surprise: It is not a triangle

Anyone who looks closely at the concept – or just reads the first paragraph on wikipedia – quickly realizes that the “triangle” has at least a fourth side: quality!
(But the term “devil’s quadrangle” has not yet found it‘s way into wikipedia)

And as handy as the tool “iron triangle” may seem in arguments, it really should be used with caution. Especially arguing about the quality constraint is very common in my experience. By relating to the “pick any two” adage people try to argue that “with the new time constraints we have to compromise on quality.“ And apart from the fact that “quick and dirty is very un-agile” this approach completely ignores the fact that compromising on quality usually does not get the job done more quickly but generates severe issues for the ensuing product.
The agile answer to this conundrum is to negotiate on scope instead of quality. That is what most sane people would do with tangible objects as well. I might go with a motorcycle (smaller scope) when developing a car isn’t feasible under existing time and budget constraints. But I definitely would not go with a car where “somewhere between 20 and 40 percent of the nuts and bolts are not tightened correctly” (less quality).

To me it seems much more rewarding to manage scope than to try to compromise on quality.

till next time
  Michael Mahlberg

2 thoughts on “Why “the iron triangle” (of project management) isn’t

  1. Hi Dominik,In my opinion there are two main reasons for the continued use of the iron-triangle-model.First of all it is compelling. It seems to be a very straightforward approach and with three variables there are only three connections and one can still consider it to be obvious in the cynefin model and doesn’t come into the combinatorial explosion – with four points that would be six connections already and considering all six points of the star-model (wich, to be fair, is also quoted in the wikipedia-article about the triangle would imply 15 possible interferences already.Secondly a lot of the people using the term do not really have a project management background but only quote the triangle to make a point.

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