EGN4034 FALL 2008DR. G.HASKINS

RISK and LIABILITY in ENGINEERING

Engineer’s Approach to Risk

Risk = Probability * Magnitude of harm

Harm = Invasion or limitation of a person’s freedom or well-being

Harm may be difficult to quantify (loss of life)

Acceptable Risk

Risk/Benefit AnalysisAR=P*M (of harm) ≤ P*M (of benefit)

Utilitarian Approach

Risk/Benefit Analysis LimitationsUnanticipated effectsQuantification difficulties (loss of life)

Inequitable distribution (risk/benefits)

Lack of informed consent

Public’s Approach to Risk

Respect for Persons Approach (rather than Utilitarian)

Informed consent Non-coerced Informed Competence to evaluate

Equity Benefits & harms equitably distributed

Public’s Approach to Risk

AR= free & informed consent+ just distribution

May substitute appropriate compensation for either of the above

Government Regulator’s Approach to Risk

AR= protecting public from harm > benefiting the public

Communication

Engineers, public and regulators have different approaches to risk

Important for engineers to take these other approaches into account when communicating “risk” to public

Risk Assessment in Practice

Involves an uncertain assessment of the probability of harm

Fault tree (fig. 7.1) Begin with undesirable event Reason back to events that might have

caused this Systematic of failure modes

Risk Assessment in Practice

Event Tree Analysis (fig. 7.2) Reason forward to examine consequences

of event Probability= product of probabilities in legs

of diagram

Limitations Unanticipated problems Human error Conjectural probablities

Tight Coupling & Complex Interactions

Tight Coupling Time is of the essence

Complex Interactions System parts may interact in unanticipated

ways

TC+CI Unanticipated failures with little time to

correct Boiler explosion NYTel

Normalizing Deviance

Increasing allowable deviation from proper standards of safety and acceptable risk

Liability for Risk

Tort Liability (standard of proof) Preponderance of the evidence ∆ violated legal duty π suffered injuries ∆’s violation of duty caused π’s injuries ∆’s violation of duty was proximate cause of π’s injuries

SOP < scientific SOP < criminal SOP