Most fields require very high probabilities of safety, even when the stakes are much lower than the extinction of humanity.[1] Here are a few examples with risk thresholds expressed in Log Odds (base 10).
Intro to Log Odds
Instead of writing probabilities like 0.9999 which is hard to read, I'll use log odds.
So LogOdds
Conversion Trick: rounding LogOdds towards zero[2] roughly corresponds to the number of nines/zeros after the dot in the probability. Conveniently, the complementary probability in log space is just negative. LogOddsLogOdds(p)
Target Reliability Table (excluding earthquake, tsunami, and extraordinary events) Annual probability of various types of failure.
sudden, widespread progression of damage
Types of Failure | Risk Categories | |||
I[4] | II[5] | III[6] | IV[7] | |
-3.90 | -4.52 | -4.90 | -5.30 | |
-4.52 | -5.30 | -5.70 | -6.15 | |
-5.30 | -6.15 | -6.60 | -7.00 |
Lifetime Reliability Target ()
LogOdds: -3.63 lifetime reliability (-5.51 annual, for a typical 75 year service life)
Piecewise log-log fatality-probability guidelines. (-1 slope represents constant Annualized Life Loss)
ALARP = As Low As Reasonably Practicable
"ALARP is now considered to apply anywhere on the risk portrayal chart"
1/16 annual chance of collapse was unacceptable
LogOdds: -1.18
Reference Periods | Reliability Classes | ||
RC1[10] | RC2[11] | RC3[12] | |
1 year | -4.87 | -5.89 | -7.00 |
50 years | -3.32 | -4.14 | -5.07 |
Log-log death-frequency target for 2050
Type of failure | Safety Class | ||
Class III[13] | Class II[14] | Class I[15] | |
Ductile (gradual) | -2.46 | -3.16 | -3.97 |
Brittle (sudden) | -3.16 | -3.97 | -4.87 |
Type of failure | Safety Class | ||
Class III[16] | Class II[17] | Class I[18] | |
Ductile (gradual) | -3.97 | -4.87 | -5.89 |
Brittle (sudden) | -4.87 | -5.89 | -7.00 |
ASIL | Examples | Target Failure Rate per Hour |
B | Headlights, Brake Lights | -7 |
C | Cruise Control, Rear Wheel Brakes | -7 |
D | All Wheel Brakes | -8 |
Effects | Severity (LogOdds Range) | |||
Minor (-3 to -5) | Major (-5 to -7) | Hazardous (-7 to -9) | Catastrophic (less than -9) | |
Airplane (reduction in functional capabilities or safety margins) | Slight | Significant | Large | Normally hull loss |
Crew | Slight increase in workload | A physical discomfort or significant increase in workload or in conditions impairing the efficiency of the flight-crew | Physical distress or excessive workload such that flight-crew cannot be relied upon to perform their tasks accurately or completely | Fatalities or incapacitation |
Passengers | Physical discomfort | Physical distress, possibly including injuries | Serious or fatal injury to a small number of persons | Multiple fatalities |
Risk per launch to | Overall | Most Endangered Individual |
Operations Personnel | -3.7 | -5 |
The Public | -4 | -6 |
Risk per launch to:
Country/Org | Page | Event Frequency/Year | |
Core Damage | Large Release | ||
INSAG | 11 | -5 | -6 |
United States | 14[19] | -4 | -5 |
Russia | 26 | -5 | -7 |
France | 17 | -5 | -7 |
Japan | 23 | -4 | -5 |
Finland | 18 | -5 | -6.3 |
Canada | 22 | -5 | -6 |
Initiating Fault Frequency | Basic Safety (mSv) | ||
Limit | Objective | ||
On-site | > -3 | 20 | 0.1 |
-3 to -4 | 200 | 0.1 | |
< -4 | 500 | 0.1 | |
Off-site | > -3 | 1 | 0.01 |
-3 to -4 | 10 | 0.01 | |
< -4 | 100 | 0.01 |
Excess lifetime risk at : -5
Living <50km from plant: -4
General Public: -6
SIL | Low Demand Mode[21] Max Probability of Failure on Demand | High Demand or Continuous Mode[22] Max Probability of Dangerous Failure per Hour |
1 | -1 | -5 |
2 | -2 | -6 |
3 | -3 | -7 |
4 | -4 | -8 |
5 sigma statistical significance (usually single-tailed): 6.54
My Ideological Conclusion (optional)
Things I don't want:
What I'd like to convey:
If useful to this report, I'm open to adding:
Inspired by Rob Miles on Doom Debates
Round positive values down. Round negative values up. trunc()
in programming.
Minimum Design Loads and Associated Criteria for Buildings and Other Structures published by the American Society of Civil Engineers (ASCE) and its Structural Engineering Institute (SEI).
Storage Sheds, Temporary Structures, Low Occupancy, Low-Risk Structures
Homes, Businesses, Most Structures, Standard Occupancy Dwellings
Schools, Gathering Places, Public Utilities, High Occupancy Gathering Halls
Hospitals, Emergency Utilities, Sensitive Occupancy, High Risk Structures
where is the CDF of the standard normal distribution
Agricultural buildings where people do not normally enter. (e.g. storage buildings, greenhouses)
Public buildings where consequences of failure are medium. (e.g. residential, office buildings)
Public buildings where consequences of failure are high. (e.g. grandstands, concert halls)
Small or temporary storage buildings
Ordinary residential buildings and office buildings
Large-scale public buildings
Rural tunnels ≤1000 m, construction access tunnels
2-lane urban tunnels, rural tunnels >1000 m
Expressways, multi-arch tunnels, tunnels ≥3 lanes or ≥3000 m
US Nuclear Regulatory Commission (USNRC) Safety Goal Policy established Quantitative Health Objectives (QHOs) that plant-attributable risk of cancer/early fatalities should be less than 0.1% of respective background risk. OECD/NEA evaluated baselines in 1980s US to extrapolate absolute risks, which continue to be referenced and haven't been rebaselined.
International Council for Harmonization (ICH) of Technical Requirements for Pharmaceuticals for Human Use: Assessment and Control of DNA Reactive (Mutagenic) Impurities in Pharmaceuticals To Limit Potential Carcinogenic Risk - M7(R1)
deployed ≤1 time per year
deployed >1 time per year