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(i.e., when an improving, “good,” project degrades, “goes bad”) or vice versa. Project trajectories
that are monotonically improving or monotonically degrading (e.g., Figure 8) do not describe
trajectory reversal. However, our study of large complex construction projects such as nuclear
power plants indicate that trajectory reversal is an important issue. If project resources and
productivity are limited and fixed, the basic project tipping point structure described above
cannot endogenously simulate projects with trajectory reversal. This is because the structure
lacks a mechanism to shift feedback loop dominance from loop B1 to R1. Exogenous
influences, additional endogenous dynamic structures, or both, are required to propel projects
beyond the tipping point and reverse their trajectory. 10
Exogenous Influences on Tipping Point Dynamics
Exogenous factors can influence the rework fraction or add-new-tasks strength, such as
changes in project scope during construction or, as with the case of the nuclear plant, changes
in requirements. An inspection of equation (5) shows that, if a project starts far enough away
from its tipping point (e.g. FRW (snt+1)