Risk

Risk

Risk is a measure for the expectation of undesirable outcome has attribute::impact to realise. This expectation concerns both the has attribute::likelihood and magnitude of the undesired outcome. Quantified levels of risk are often used to enable an assessment of risk in order to establish if they fall within acceptable limits or to determine which risks pose the highest has attribute::threat.

Definitions

There is no one, universally accepted definition for risk. A prominent definition of risk is provided in the ISO 31000:2009 risk management standard , where risk is defined as the ‘effect of uncertainty on objectives’ and both positive and negative effects are included. As this definition is of a high conceptual level and can be counter-intuitive, for the purpose of this wiki, the definition as mentioned above will be used.

Objective and subjective risk

There are two aspects of the determination of risks: the risks that are in fact present (objective risks), and the risks as they are perceived (subjective risks). One would expect the two to be very similar, but studies have shown they can (and often do) differ quite a bit.

About subjective risk

Results from urban planning decisions can influence citizens’ perception of risk including the distraction of risk perception for more objective risk levels. Conversely, citizens’ risk perception can result in societal demands on urban planning. Several specific aspects as addressed in the following are worth consideration in strategic urban planning. These aspects among others include indicators for citizens’ subjective perception of criticality of infrastructure and need to protect it, including by appropriate urban planning measures. Conversely, infrastructure that results from urban planning may also influence subjective assessment of its criticality and contribution to security or susceptibility to natural or anthropogenic (“man made”) risk.

Risk perception is strongly influenced by various subjective factors that drag it from objective risk figures. Factors such as overconfidence, loss aversion, individual experience, temporal factors, capacity of remembering, level of information and knowledge, public discourse, stigmatization, cultural factors, orientation of values, confidence in institutions, etc.

Adequate risk management and adequate public communication can help urban planners to prevent negative effects from public risk (mis-)perception and related public demands on or acceptance of urban design. Addressing of risk in planning should be coherent with societal risk perception and views.

To do so, the complexity of individual and social mechanisms of risk perception has to be appreciated. Humans usually do not fear statistically highly ranked threats to life and health (such as car accidents, food poisoning, cancer and others), whereas they are disproportionately wary of spectacular hazards, even if related vulnerabilities are low.

About objective risk

Although terminology may vary, two widely accepted elements in the definition of risk are the inclusion of likelihood and magnitude and to a lesser extent, the fact that to arrive at a measure of risk, the two should be multiplied. A simple, but widely used definition of risk is therefore

Risk = Likelihood of event realizing X Impact (expected loss in case the accident realizes).

Many variations exist, for example by distinguishing between the likelihood of a threat realizing (also called probability) and the likelihood that that threat will affect an object (has attribute::vulnerability). An example would be storm damage: the probability would reflect the likelihood of a storm at the object, the vulnerability would reflect the likelihood that this storm would cause damage and the impact would reflect the extent of damage that would occur if the storm would cause damage. The quantified risk formula associated with this definition is

Risk = Likelihood of event realizing X vulnerability (probability of realized event impacting object) X Impact (expected loss in case the accident realizes and impacting object).

The estimation of likelihood in security

The use of probability relies on the ability to make reliable predictions. This is most often based on the analysis of past occurrences and identification of trends. When determining risk in the field of threats related to is caused by::human intent, the use of trend analysis to determine likelihood is criticised for threats actively seeking harm (for example terrorism). This is due to the fact that

• these events occur relatively infrequently, making the recognition of trends difficult;
• in contrast to for instance natural threats, the results of past events does influence the likelihood of future events: potential perpetrators will actively seek ‘the weakest link’. This means that the predicting value of trends in past occurrences is in doubt.

A way to overcome these problems is to substitute has attribute::attractivity for probability and has attribute::conceivability for vulnerability. In this way, assumptions about historical data predicting future events can be avoided.

Uses of risk assessment

t.b.d.

Sources of risk

One way to typify types of risk, is by their causes. A cause for risk is called a is caused by::threat. Threats can be classified into has attribute::safety threats, consisting of natural threats, is caused by::human failure, is caused by::technical failure, is caused by::failure of critical services and has attribute::security threats which are due to is caused by::human intent.

Perception of risk and affecting factors

What people perceive, is real for them; so their behaviour will be influenced not by the actual level of security, but of their perception of it.

This is relevant to urban planners since they have some means to direct the perceived security or at the very least has means to predict it and account for it in planning. Addressing of risk in planning should be coherent with societal risk perception and views (cf. OECD 2003: 54-56). Adequate risk management and public communication can help urban planners to prevent negative effects from public risk perception, or misperception, and related public demands on or acceptance of urban design. However, effects of urban planning decisions can also distract citizens’ risk perception from more objective risk levels.

Factors that affect the individual and social perception of risk:

• Voluntariness

Risks from activities considered to be involuntary or imposed (for example, exposure to chemicals and radiation from a terrorist attack using chemical weapons or dirty bombs) are judged to be greater, and are therefore less readily accepted, than risks from voluntary activities (such as smoking, sunbathing or mountain climbing).

• Controllability

Risks from activities considered to be under the control of others (such as the release of nerve gas in a coordinated series of terrorist attacks) are judged to be greater, and are less readily accepted than those from activities considered to be under the control of the individual (such as driving an automobile or riding a bicycle).

• Familiarity

Risks resulting from activities viewed as unfamiliar (such as travel leading to exposure to exotic-sounding infectious diseases) are judged greater than risks resulting from activities viewed as familiar (such as household work).

• Fairness

Risks from activities believed to be unfair or to involve unfair processes (such as inequities in the location of medical facilities) are judged greater than risks from “fair” activities (such as widespread vaccinations).

• Benefits

Risks from activities that seem to have unclear, questionable or diffused personal or economic benefits (for example, proximity to waste-disposal facilities) are judged to be greater than risks resulting from activities with clear benefits (for example, employment or automobile driving).

• Catastrophic potential

Risks from activities associated with potentially high numbers of deaths and injuries grouped in time and space (for example, major terrorist attacks using biological, chemical or nuclear weapons) are judged to be greater than risks from activities that cause deaths and injuries scattered (often apparently randomly) in time and space (for example, household accidents).

• Understanding

Poorly understood risks (such as the health effects of long-term exposure to low doses of toxic chemicals or radiation) are judged to be greater than risks that are well understood or self-explanatory (such as pedestrian accidents or slipping on ice).

• Uncertainty

Risks that are relatively unknown or highly uncertain (such as those associated with genetic engineering) are judged to be greater than risks from activities that appear to be relatively well known to science (such as actuarial risk data related to automobile accidents).

• Effects on children

Activities that appear to put children specifically at risk (such as drinking milk contaminated with radiation or toxic chemicals or pregnant women exposed to radiation or toxic chemicals) are judged to carry greater risks than more-general activities (such as employment).

• Victim identity

Risks from activities that produce identifiable victims (such as an individual worker exposed to high levels of toxic chemicals or radiation, or a child who falls down a well) are judged to be greater than risks from activities that produce statistical victim profiles (such as automobile accidents).

• Dread

Risks from activities that evoke fear, terror or anxiety due to the horrific consequences of exposure (for example to HIV, radiation sickness, cancer, Ebola or smallpox) are judged to be greater than risks from activities that do not arouse such feelings or emotions regarding exposure (for example to common colds or household accidents).

• Trust

Risks from activities associated with individuals, institutions or organizations lacking in trust and credibility (for example, chemical companies or nuclear power plants with poor safety records) are judged to be greater than risks from activities associated with trustworthy and credible sources (for example, regulatory agencies that achieve high levels of compliance from regulated industries).

• Media attention

Risks from activities that generate considerable media attention (such as anthrax attacks using the postal system or accidents at nuclear power plants) are judged to be greater than risks from activities that generate little media attention (such as occupational accidents).

• Accident history

Activities with a history of major accidents or incidents, or frequent minor accidents or incidents (such as leaks from waste-disposal facilities) are judged to carry greater risks than activities with little or no such history (such as recombinant DNA experimentation).

• Reversibility

The risks of potentially irreversible adverse effects (such as birth defects from exposure to a toxic substance or radiation) are judged to be greater than risks considered to be reversible (for example, sports injuries).

• Personal stake

Activities viewed as placing people or their families personally and directly at risk (such as living near a waste-disposal site) are judged to carry greater risks than activities that appear to pose no direct or personal threat (such as the disposal of waste in remote areas).

• Ethical and moral status

Risks from activities believed to be ethically objectionable or morally wrong (such as providing diluted or outdated vaccines for an economically distressed community) are judged to be greater than the risks from ethically neutral activities (such as the side-effects of medication).

• Human versus natural origin

Risks generated by human action, failure or incompetence (such as negligence, inadequate safeguards or operator error) are judged to be greater than risks believed to be caused by nature or “acts of god” (such as exposure to geological radon or cosmic rays).”

Related subjects

Risk analysis Risk assessment Health risks

MAP

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