Precondition for Unsafe Act¶
Name the immediate situational, personal, and team conditions — fatigue, distraction, a steep authority gradient — that raise the probability of frontline operator error, a distinct HFACS layer between upstream supervision and the unsafe act itself.
Core Idea¶
A precondition for unsafe act is the HFACS layer sitting between the supervisory layers above and the unsafe act below, naming the immediate situational, personal, and team conditions that substantially elevate the probability of frontline operator error at the moment of action. Its commitment is that operator reliability is a function of state, not fixed skill: HFACS partitions the layer into conditions of the operator (adverse mental and physiological states, limitations) and personnel factors (CRM failures, personal readiness). It decouples operator state from operator action.
Scope of Application¶
The layer lives across the accident-investigation subfields of safety and human-factors practice — the substrate-class of safety-managed sociotechnical systems with frontline operators.
- Aviation safety — HFACS's birthplace: fatigue, unfamiliar crew pairing, authority gradient.
- Healthcare and patient safety — HFACS-medical: surgeon fatigue, team unfamiliarity, distraction.
- Nuclear and process safety — operator conditions immediately preceding the active failure.
- Financial operations — the less-canonical adaptation for trading and middle-office operator error.
Clarity¶
Naming this layer gives the investigator a place for findings — a long shift, an unfamiliar pairing, a steep authority gradient — that otherwise read as colour around the "real" cause and get folded into a blame verdict. It sharpens the layer-attribution question: was this a condition the operator was in, the act taken, or an arrangement laid down upstream? And it tells the practitioner the corrective belongs at the precondition layer, not the act below or organisation above.
Manages Complexity¶
An effectively unbounded, never-repeating list of what can be "going on" with an operator maps onto a small fixed typology: five slots across two sub-layers. Irreproducible situational details become comparable, trendable tokens. The analyst tracks two coordinates per finding — which layer, which slot — under one fixed reading: a precondition is a probability shift, not a determinant. A layer cut then a slot cut decides where the corrective belongs, and the interventions are slot-indexed.
Abstract Reasoning¶
The layer licenses a diagnostic with a probabilistic, not deterministic, reading (elevated odds, never the error itself), an interventionist move with slot-indexed remedies and an explicit negative prediction, boundary-drawing on the layer-attribution cut and the immediacy test against latent conditions, and an upstream-causal trace showing preconditions are produced by the supervision and organisation above, so leaving those intact regenerates the precondition.
Knowledge Transfer¶
Within safety and human-factors practice the precondition layer transfers as mechanism, completing the HFACS quartet, with the five-slot typology, the probability-shift reading, the immediacy test, the upstream trace, and the slot-indexed countermeasures carrying unchanged across aviation, medicine, nuclear, and finance — because these are four applications of one framework to a single substrate-class, not distinct substrates. Beyond it, the general pattern (the actor's state shifts error probability) is owned by the parents context_dependence, Cognitive Load, Attention, and state; the HFACS typology and slot-indexed vocabulary stay home.
Relationships to Other Abstractions¶
Current abstraction Precondition for Unsafe Act Domain-specific
Parents (2) — outgoing typed relations
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Precondition for Unsafe Act presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) Prime
The HFACS precondition stratum presupposes the Swiss-cheese layered model that distinguishes an operator's immediate state from the active act below and latent organizational holes above.
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Precondition for Unsafe Act is a decomposition of Context Prime
A precondition for unsafe act is context specialized to the immediate operator-and-team surround that changes what a fixed capability or action does by shifting the probability of error at the sharp end.
Children (1) — abstractions linked here by typed relations
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Human Factors Analysis and Classification System Domain-specific includes Precondition for Unsafe Act
Preconditions for unsafe acts are the third constituent stratum of HFACS.
Hierarchy paths (26) — routes to 10 parentless roots
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → is a kind of Conjunctive Path Activation → presupposes, typical Causality → is a kind of Dependency
- Precondition for Unsafe Act → is a decomposition of Context
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → presupposes Redundancy → is a decomposition of Self Checking
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → is a kind of Defense In Depth → is a kind of, typical Redundancy → is a decomposition of Self Checking
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → presupposes Redundancy → is a kind of Reserve → is a decomposition of Mobilization → presupposes Latent Realizable Capacity
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → presupposes Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Optimization
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → presupposes Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Locality Of Reference → presupposes Heavy-Tailed Distributions
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → is a kind of Defense In Depth → is a kind of, typical Redundancy → is a kind of Reserve → is a decomposition of Mobilization → presupposes Latent Realizable Capacity
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → is a kind of Defense In Depth → is a kind of, typical Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Optimization
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → presupposes Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Locality Of Reference → is a kind of Recurrence
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → presupposes Redundancy → is a kind of Reserve → is a decomposition of Economy Of Force → is a kind of Allocation → presupposes Scarcity → is a decomposition of Constraint
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → is a kind of Defense In Depth → is a kind of, typical Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Locality Of Reference → presupposes Heavy-Tailed Distributions
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → presupposes Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Reserve → is a decomposition of Mobilization → presupposes Latent Realizable Capacity
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → is a kind of Defense In Depth → is a kind of, typical Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Locality Of Reference → is a kind of Recurrence
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → is a kind of Defense In Depth → is a kind of, typical Redundancy → is a kind of Reserve → is a decomposition of Economy Of Force → is a kind of Allocation → presupposes Scarcity → is a decomposition of Constraint
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → is a kind of Defense In Depth → is a kind of, typical Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Reserve → is a decomposition of Mobilization → presupposes Latent Realizable Capacity
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → presupposes Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Locality Of Reference → is a decomposition of Spatial Indexing → is a kind of Search and Retrieval → presupposes Trade-offs → presupposes Constraint
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → presupposes Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Reserve → is a decomposition of Economy Of Force → is a kind of Allocation → presupposes Scarcity → is a decomposition of Constraint
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → presupposes Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Locality Of Reference → is a decomposition of Spatial Indexing → is a kind of Search and Retrieval → presupposes Problem Space → is a kind of Representation → presupposes Abstraction
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → is a kind of Defense In Depth → is a kind of, typical Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Locality Of Reference → is a decomposition of Spatial Indexing → is a kind of Search and Retrieval → presupposes Trade-offs → presupposes Constraint
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → is a kind of Defense In Depth → is a kind of, typical Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Reserve → is a decomposition of Economy Of Force → is a kind of Allocation → presupposes Scarcity → is a decomposition of Constraint
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → presupposes Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Locality Of Reference → is a decomposition of Spatial Indexing → is a kind of Search and Retrieval → presupposes Problem Space → is a decomposition of State and State Transition → includes Phase Space
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → is a kind of Defense In Depth → is a kind of, typical Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Locality Of Reference → is a decomposition of Spatial Indexing → is a kind of Search and Retrieval → presupposes Problem Space → is a kind of Representation → presupposes Abstraction
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → presupposes Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Locality Of Reference → is a decomposition of Spatial Indexing → is a kind of Search and Retrieval → presupposes Problem Space → presupposes Problem Representation → is a kind of Representation → presupposes Abstraction
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → is a kind of Defense In Depth → is a kind of, typical Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Locality Of Reference → is a decomposition of Spatial Indexing → is a kind of Search and Retrieval → presupposes Problem Space → is a decomposition of State and State Transition → includes Phase Space
- Precondition for Unsafe Act → presupposes Swiss Cheese Model (Layered Defense with Aligning Holes) → is a kind of Defense In Depth → is a kind of, typical Redundancy → is a decomposition of Two-Store Architecture → presupposes, typical Caching → presupposes Locality Of Reference → is a decomposition of Spatial Indexing → is a kind of Search and Retrieval → presupposes Problem Space → presupposes Problem Representation → is a kind of Representation → presupposes Abstraction
Neighborhood in Abstraction Space¶
Precondition for Unsafe Act sits in a moderately populated region (56th percentile for distinctiveness): it has near-neighbors but no dense thicket of look-alikes.
Family — Organizational & Operational Failure Modes (38 abstractions)
Nearest neighbors
- Active Failure — 0.86
- Crew resource management — 0.86
- Automation Bias — 0.86
- Latent Condition — 0.85
- Operator-Vigilance Dependency — 0.85
Computed from structural-signature embeddings · 2026-10-25