The Buffer Fever Chart is a tool that is used extensively in TameFlow and in Critical Chain Project Management (CCPM) used in the Theory of Constraints. For an introduction about the topic, see the earlier posts:
If the rules for drawing the Red, Yellow, and Green zones are “guidelines” or “empirical”, then doesn’t that mean they are not accurate indications of project status?
Why not use the more accurate CC PM measures from dynamic buffers, or buffer protection (not penetration, which is what fever charts use)?
CCPM buffers in Tameflow are a project execution construct that comes for free! In that sense they are not used as protection mechanism that are paid for (Like a Donald Reinertsen context where you trade money for protection)
In both the “Hyper” book and in the “Tame your Work Flow” we clearly show how the MOVE Buffer is the equivalent of a CCPM buffer. The underlying logic is exactly the same.
In the “Hyper” book I do refer to the works of Geekie (2006), Fallah (2010) and Cox (2010) for using dynamic buffer sizing, stating clearly that those are more advanced techniques. (You might want to check the TameFlow Bibliography for the exact references.)
Furthermore, the point of positioning and sizing the buffer is not a matter of accuracy. How we work in #tameflow is not by contemplating an “accurate project status” - but by detecting actionable Work Execution Signals. Such signals can be buffer zone transition events (but there are others too, which are not present in #TOC).
What matters is that such signals either trigger direct and immediate action by the team or escalation for Management by Exception.
If the buffer is too responsive or too relaxed, tweak the heuristic and make it tighter or wider. Find the sustainable stable state, where most of the items are in the Yellow Zone most of the time. But be prepared to discern if any unbalance is due to misplaced/sized Buffers or to the actual nature of the work. Keep an eye on the stability of the Flow Time Distributions. If they are stable, then you are not calibrating the Buffers properly. If they are changing, then there is a factual reason to consider and recalculate.
If you have the skills to exercise more sophisticated buffer placement/sizing strategies, then: Great! Use them!
But here we are trying to teach a method to an audience (those into Agile) who mostly believe that running ceremonies can address all the problems of the world. Please keep the perspective, but also be perceptive that there is ample latitude to use more sophisticated methods, if you can handle them, and are able measure and validate the further benefits they might provide.