Organizational Drift to Failure (Dekker)

Sidney Dekker's model of how organizations migrate toward catastrophe through a series of locally rational decisions that are individually defensible but collectively deadly. Unlike Vaughan's normalization of deviance (which focuses on rule violations becoming accepted), Dekker's drift model focuses on the incremental optimization of efficiency at the expense of safety margins. The mechanism: (1) production pressure creates incentive to reduce safety margins, (2) small efficiency gains are achieved by trimming what seem like excessive margins, (3) nothing bad happens, validating the trim, (4) the new, thinner margin becomes the baseline, (5) further trimming occurs from the new baseline, (6) the system drifts to the edge of the safety envelope without anyone noticing, (7) a normal perturbation that the original margins would have absorbed triggers catastrophe. The Columbia shuttle disaster exemplified this: foam strikes on the thermal protection system were systematically reinterpreted as acceptable, each reinterpretation building on the last, until the system had drifted so far from original safety margins that a normal foam strike was fatal.

When to use it

When safety margins are being trimmed for efficiency. When near-misses are treated as non-events rather than warnings. When the gap between official procedures and actual practice is widening. When organizations have been accident-free for a long time (paradoxically the highest-drift-risk period).

How it can help

Provides specific drift-detection methods. (1) Track safety margins over time—not just incidents but the distance between actual performance and safety limits. Shrinking margins are the leading indicator. (2) Maintain 'margin owners' who are incentivized to protect margins, not to optimize efficiency. (3) Periodically compare current operating parameters to original design specifications—the gap is the drift. (4) Treat near-misses as successes (we got away with it) AND as warnings (we got closer to the edge). (5) When production pressure says 'we can get away with less margin,' add the voice that says 'the last three times we trimmed margin, the edge got closer.' The key: drift is invisible at any single point in time—it's only visible as a trajectory.