Ask Art
"What is A-D-P in lean problem solving?"
What Is the A-D-P Countermeasure Hierarchy?
Short answer: A-D-P stands for Administration, Detection, Prevention — a hierarchy for evaluating the strength of operational countermeasures. I introduced it in Four Types of Problems as a way to think about countermeasures for Type 2 (gap-from-standard) problems. A is weakest, P is strongest. Beyond all three, Toyota uses mizen-boushi for pre-occurrence prevention upstream in product development.
What do A, D, and P stand for?
- A — Administration. Checklists, work instructions, training, procedures — and passive alerts like warning lights or buzzers. The countermeasure depends on a human noticing, remembering, or responding correctly. It is the weakest form because it can be ignored, forgotten, or overridden.
- D — Detection. A sensor, a switch, a signal, a device that catches the error, alerts, and stops the process — production does not continue until the fault is cleared. This is stronger than administration because it does not depend on human attention. But detection only catches the defect or error. It does not fix the source. The problem can still occur; it is just caught before it moves downstream.
- P — Prevention. The source of the cause is eliminated. The fixture will not accept the part in the wrong orientation. The process physically cannot produce the defect. There is nothing to detect because the error cannot occur.
Each level removes more dependence on human attention and judgment. A relies on the person. D relies on a device. P relies on the design of the process itself.
Where did A-D-P come from?
I introduced A-D-P in Four Types of Problems as a way to evaluate countermeasures for Type 2 problems — gap-from-standard situations where a known standard exists and something departed from it. When you solve a Type 2 problem and propose a countermeasure, the question is: how strong is it? A-D-P gives a simple gradient for answering that.
How does A-D-P relate to other frameworks?
The idea of ranking countermeasures by strength is not unique to A-D-P. Several frameworks draw similar distinctions:
- Shingo’s control vs. warning devices — Shingo split poka-yoke into warning devices (alert the operator) and control devices (prevent the error). A-D-P adds a middle layer: detection stops the process but does not eliminate the source, which Shingo’s two-way split groups with full prevention.
- 8D problem solving — the 8D process distinguishes between containment actions (D3) and permanent corrective actions (D5). Containment catches the problem and keeps it from reaching the customer, but does not fix the root cause — similar to the D layer. The permanent corrective action aims to eliminate the source — similar to P.
- Safety hierarchy of controls — industrial safety ranks controls from elimination down through engineering controls, administrative controls, and PPE. The logic is the same: reduce dependence on human behavior as you move up.
A-D-P is a simple, practical gradient for the shop floor. It does not replace any of these frameworks — it gives a quick way to evaluate whether a proposed countermeasure is administrative, detection-based, or truly preventive.
What does A-D-P not cover?
A-D-P is an operational hierarchy — it applies to countermeasures on the shop floor, in existing processes. It does not reach upstream into product development, where the process does not yet exist and the failure has not yet occurred.
That is the domain of mizen-boushi (未然防止) — pre-occurrence prevention. Mizen-boushi catches planning mistakes in design review before a part is built, by focusing on change points, changed conditions, and interfaces where problems tend to originate. It is a different layer of prevention, upstream of A-D-P, and it belongs to design and development rather than production.
A-D-P and mizen-boushi are not competitors. They are different layers of the same prevention picture — A-D-P for operational countermeasures, mizen-boushi for upstream design prevention.
See also: Is Poka-Yoke a Lean Tool, and What Does It Mean?, What’s the Difference Between Mistake-Proofing and Error-Proofing?, What Is Mizen-Boushi?, Jidoka — Part 1, and Jidoka — Part 2.