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Final StateThe Frequency-Impact Matrix: A Triage Grid Dressed as a Ruler
VOL. I  ·  NODE 102▢  ATLAS

THE GRID ON EVERY WALL

The Frequency-Impact Matrix: A Triage Grid Dressed as a Ruler

A frequency-impact matrix is a two-axis triage grid: probability on one axis, impact on the other, useful for escalation but too coarse to measure the tail.

A risk matrix shown across boardroom, hospital, and control-room settings to show how widely the grid is reused.The same coloured grid appears in different organisational contexts; the point is ubiquity, not a numerical reading from any cell.BOARDROOMHOSPITALCONTROLROOMACCEPTABLETHE SAME GRID, ON EVERY WALL

FOUR CORNERS

Four corners, not four automatic answers

Two-by-two frequency-impact matrix highlighting the rare-and-severe corner as the one that needs an owner.Frequent severe, rare cheap, and frequent cheap corners have routine responses, while the rare severe corner is singled out for escalation because colour alone cannot decide it.CONSIDERREDUCEOR TRANSFERFREQUENT &SEVERETESTAPPETITERARECHEAPCONSIDERSTANDARDISEFREQUENT +CHEAPESCALATENAME OWNERRARE, SEVERERAREFREQUENTFREQUENCYSEVERECHEAPIMPACTPROMPTS, NOTAUTOMATIC ANSWERS
  • Frequent and cheap: consider standardising or automating
  • Frequent and severe: consider reducing, transferring, or insuring
  • Rare and cheap: test whether the loss fits appetite
  • Rare and severe: escalate, unfold, price, and name an owner

Used as triage, the fourth corner is where the value has always hidden — and where the AI wins you cannot measure wait, uncounted.

BORN TO ESCALATE

A military prioritisation lineage, explicit by 1984

Risk matrix connected to an approval ladder rather than a measurement scale.The figure shows MIL-STD-882B's matrix as a qualitative prioritisation device: cells sort hazards for action and review, not into a precise value of risk.1984 · MIL-STD-882BLOWERPRIORITYREVIEWACTIONPRIORITYPROBABILITYSEVERITYQUALITATIVE PRIORITYMANAGEMENT SETSTHE THRESHOLD
  • MIL-STD-882B (1984): sample severity × probability matrices
  • The output was a qualitative priority code, not measured loss
  • The managing activity set the acceptable-risk threshold and disposition

In that lineage, the grid focused management attention; it did not supply the decision — a way to decide what needs review, not how much risk exists.

THE COMPUTATION

…the quantum of risk is placed on one scale and the sacrifice involved in the measures necessary for averting the risk … is placed in the other; and … if it be shown that there is a gross disproportion between them … the defendants discharge the onus on them.

Lord Justice Asquith, Edwards v. National Coal Board, 1949

The seed of every later decision rule for the rare-and-severe band — and the reason a recognised latent exposure demands an answer, not a colour.

AS LOW AS REASONABLY PRACTICABLE

A rule the colour never was

ALARP tolerability column with intolerable, tolerable-if-reduced, and broadly acceptable bands.The column contrasts a rule with a colour: in the tolerable region, the duty-holder must justify why further reduction would be grossly disproportionate.INTOLERABLERISK REDUCTIONREQUIREDTOLERABLE IF ALARPTEST FURTHERCONTROLSBROADLYACCEPTABLEMAINTAIN CONTROLSHARMNEXT CONTROLGROSSDISPRO-PORTIONALARP SHOWN?THE DUTY-HOLDERMUST JUSTIFYTHE NEXT MEASURE
  • Three regions: unacceptable / tolerable only if ALARP / broadly acceptable
  • In the middle, implement further controls unless their sacrifice is grossly disproportionate to the risk reduction
  • The duty-holder must show why further reasonably practicable measures are not required

A demonstration is documented reasoning about specific measures and their cost, not a filled-in square — which is why a colour points nowhere and a rule points forward.

UNFOLD THE CELL

Unfold the cell into owned barriers

  1. 01Put the top event in the middle
  2. 02Threats to the left, consequences to the right
  3. 03A barrier on every path — preventive left, mitigating right
  4. 04Each barrier: an owner and a test date
  5. 05Name the scenario or premortem that tests the path

The natural next step after recognising a latent exposure: a barrier left to rot is itself a weak signal worth watching.

Bowtie diagram with threats, top event, consequences, barriers, owners, and test dates.The figure unfolds a single matrix cell into the apparatus a decision needs: barriers on every path, named owners, test dates, and a scenario to rehearse.THREATSCONSEQUENCESTOPEVENTHALETEST 03/26OKAFORTEST 05/26LIUTEST 01/26PREVENTIVEVOSSTEST 04/26SATOTEST 02/26MITIGATINGNO OWNERAN OWNER + TEST DATEON EVERY BARRIER

ONE LINE INSTEAD

Replace the buckets with a curve

Loss-exceedance curve showing probability of losses above an amount against an appetite line.The illustrative figure replaces bucket colours with a continuous curve, making a hypothetical tail and probability-tolerance line visible without presenting the example values as observed data.ILLUSTRATIVENOT OBSERVED DATA€200K€2M€20MANNUAL LOSSCHANCE OF EXCEEDING10% CHANCEOF LOSING > €2M1% CHANCEOF LOSING > €20MTOLERANCEMAX EXCEEDANCECHANCECURVE STAYS UNDERTHE LINE?
Illustrative loss-exceedance curve; values are examples, not observed data. Farmer (1967) is an early risk-criterion precursor; Hubbard & Seiersen (2016) advocate quantitative alternatives to matrices.

One line, no range compression — and it can finally prove an averted loss with a curve, not an anecdote.

  • Loss along the bottom, annual chance of exceeding it up the side
  • Illustrative points: 10% above €2M; 1% above €20M
  • Overlay a tolerance line, then compare the full loss profile

BOTH WAYS AT ONCE

The grid runs both ways

Mirrored matrix showing threats on one side and opportunities on the other.The figure makes Hillson's sign flip visible: threat responses mirror opportunity responses, so the same silent corner can hide downside and upside.FREQUENTRARETHREATSHOW LIKELYHOW HARMFULOPPORTUNITIESHOW LIKELYHOW RICHRARE +SEVERERARE +RICHAVOIDEXPLOITTRANSFERSHARETHE SAME CORNERTHE OPPOSITE SIGN
  • Hillson, 2002: extend one risk process to threats and opportunities
  • Threats on the left, opportunities on the right
  • Paired responses include avoid / exploit and transfer / share

The windfall wing is a field of real options no process is watching for — the same corner, the same silence, the opposite sign.

The cell is the question, not the answer.

In 2008 a decision scientist showed a five-by-five can rank a rare catastrophe worse than chance; the theorem's detail lives in range compression.

THE APPARATUS THAT DECIDES

Keep the triage. Replace the verdict.

  • Use the grid only for triage and escalation
  • Add the rule, barrier owner, loss profile, and scenario
  • Operator test: no owner, test date, curve, or scenario means the cell is still open

What is new here is the apparatus behind the colour: lineage, rule, owner, curve, and scenario. The corner they govern is not fixed ground: it is a price that moves. Back to the cell that is not a decision.

Read the transcript

01 · THE GRID ON EVERY WALL

Start with the tool itself, not the boardroom drama. A frequency-impact matrix is a two-axis triage grid: probability on one side, impact on the other. Its legitimate job is cheap sorting and escalation. Its common misuse is to be read as measurement. This pass asks where the grid came from, what it can safely do, and which extra apparatus has to take over when the marked cell could end you.

02 · FOUR CORNERS

The four corners are a sorting vocabulary, not four verdicts. Frequent and cheap may be candidates for standardisation or automation. Frequent and severe may call for reduction, transfer, or insurance. Rare and cheap still has to fit the organisation's appetite. Rare and severe should not be waved through because it has a colour. It should be escalated, unfolded, priced, and owned. The matrix can point to that work. It cannot replace it.

03 · BORN TO ESCALATE

One important lineage is military, not the only origin story. In 1984, revision B of United States military standard eight eighty-two included sample matrices that combined hazard severity with hazard probability. The result was a qualitative priority code. The managing activity still had to define which risks were unacceptable, decide what action followed, and accept or reject the disposition. That is narrower than measurement. The matrix focused management attention; it did not calculate a precise likelihood, price the loss, or decide the control. It was a prioritisation device drawn on graph paper.

04 · THE COMPUTATION

Britain took a different road. In 1949, a coal miner's widow sued the National Coal Board, and the judgment supplied a durable test. Reducing a risk is required so far as is reasonably practicable. Reasonably practicable, said the court, means placing the risk on one scale and the sacrifice involved in further measures on the other. A measure may be ruled out when that sacrifice is grossly disproportionate to the risk reduction. The burden is on the duty-holder to make that case. A colour orders nothing. This test asks for the next measure and the reason for stopping.

05 · AS LOW AS REASONABLY PRACTICABLE

The rule is commonly expressed as as low as reasonably practicable. A L A R P. The Health and Safety Executive's tolerability framework separates three regions. At the top, risk is generally unacceptable and reduction is required. At the bottom, risk is broadly acceptable, while existing controls still have to be maintained. In the wide middle, risk is tolerable only if it has been reduced as low as reasonably practicable. Further measures are expected unless their sacrifice would be grossly disproportionate to the reduction achieved. Notice what this adds to a coloured cell: a duty to examine specific controls and justify why the next one is not reasonably practicable.

06 · UNFOLD THE CELL

The rule tests whether more reduction is reasonably practicable. A second form shows what the cell contains, and it looks like a bowtie. Put the top event in the middle: the moment control is lost. Draw the threats that could lead to it on the left and the consequences on the right. Put preventive barriers before the event and mitigating barriers after it. Then make the diagram operational: every barrier gets an owner, a last-tested date, and a scenario or premortem that exercises the path. Published histories commonly associate bowties with late twentieth-century chemical and offshore safety practice, but the exact origin story is not needed for the method. You may not know the exact odds. You can still see that barrier three has no owner.

07 · ONE LINE INSTEAD

A quantitative alternative replaces the buckets with a loss-exceedance curve. Loss runs along the bottom. Up the side is the annual chance of exceeding that loss. The points in this exhibit are illustrative, not observed data: suppose the model estimates a ten percent chance of losses above two million euros, and a one percent chance above twenty million. A tolerance line can then state the maximum exceedance probability allowed at that part of the loss range. Farmer's 1967 nuclear-siting curve is an early precursor in plotting consequence against probability; later quantitative-risk authors have argued for continuous alternatives to matrices. The gain is not certainty. It is seeing the modeled tail, the assumptions, and the tolerance without hiding them in bins.

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09 · BOTH WAYS AT ONCE

And the process can run both ways. In 2002, David Hillson argued for extending risk management so that one process handles both threats and opportunities. A mirrored matrix makes the proposal visible. Threats sit on one side, by likelihood and harm. Opportunities sit on the other, by likelihood and benefit. Some response strategies pair: avoid a threat or exploit an opportunity; transfer a threat or share an opportunity. This does not prove that every upside is a negative threat. It means the same governance process can ask about both signs. The rare severe corner then has an upside counterpart: a large opportunity no routine is watching for.

10 · THE QUESTION, NOT THE ANSWER

Here is the thing to carry away from sixty years of argument. The matrix remains useful at the first pass, when the job is to sort cheaply and escalate. Past that pass it changes status. It is not the decision object. It is an index card telling you which apparatus to bring next: the rule, the owner, the price curve, the scenario. The cell is the question, not the answer.

11 · THE APPARATUS THAT DECIDES

Leave with the distinction. The grid may stay on the wall as a first-pass sorter, but the decision object is the apparatus attached to the marked cell. A L A R P supplies a rule for further controls. The bowtie names barriers and owners. The loss curve exposes a modeled profile in money and probability. The premortem supplies a scenario. Operator's test: if the cell has none of these, it is still open. Keep the triage. Replace the verdict.

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