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Introducing engineering
Introducing engineering

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3.8 Engineering risk

Risk is a word that seems to be ever present in the language of both the engineering profession and the general public.

I will try to define the term risk later, but any observer of the TV and news media will probably have noticed an increasing demand from the public for proper explanations about how specific risks are regulated; in fields as diverse as finance, health and personal relations. In 2011, there were two stories that both caused widespread public debate about the risks involved; the Fukushima nuclear reactor melt down following the earthquake and tsunami, and the motorway (M5) pile-up in the UK, originally thought to have been caused by bonfire smoke but later evidence proved that it was thick fog. In the past, such issues rarely surfaced outside technical or specialist circles. Activities were either safe or unsafe. Indeed, this simple approach still features largely in both the public imagination and some newspaper articles. But most of us now realise that the world cannot easily be described in such absolute terms, and the safety we seek is constantly balanced against the benefits we desire. Perhaps a good example here is driving. All drivers think of their driving as safe, but most of us have performed an overtaking or other manoeuvre which, in retrospect, we considered 'risky'. What I want to do in this section is to investigate how we can identify, assess, and manage risks, and identify what part engineers have to play in this process.

The role of the engineer, in identifying and managing risks, has been recognised by the engineering profession. Among its aims and objectives, the UK's Engineering Council stresses the importance of a proper balance between efficiency, public safety and the needs of the environment when carrying out engineering activities. The Council's guidance for the institutional codes of conduct expects engineers to address risk thoroughly – applying in-depth, long-term thinking – so that they may help to encourage greater awareness of risk in others with whom they work. The key elements of the Council's Guidance on Risk (2011) are listed below.

  1. Apply professional and responsible judgement and take a leadership role.
  2. Adopt a systematic and holistic approach to risk identification, assessment and management.
  3. Comply with legislation and codes, but be prepared to seek further improvements.
  4. Ensure good communication with the others involved.
  5. Ensure that lasting systems for oversight and scrutiny are in place.
  6. Contribute to public awareness of risk.

Many serious incidents are the result of component or structural failure, but often there is some human error involved as well. Often it is difficult to separate more technical engineering issues from human factors – so-called 'hard' and 'soft' elements respectively. Likewise, perceptions of the relative significance of many of these issues is a personal one.

Activity 28 (exploratory)

You may like to test some of your perceptions of risk now with the following activity that relates to some commonly held views. Do you believe the following statements are true or false?

  • Butter is the best first aid treatment for a burn.
  • Accidents are due to the inevitability of statistical laws.
  • The main danger from a gas leak is asphyxiation.
  • A small vehicle can stop more quickly than a large one.
  • Lightning does not strike twice in the same place.
  • A silver spoon turns black in contact with poisonous toadstools.
  • A tourniquet is the best method for stopping bleeding from a wound.
  • Accidents happen to other people.
  • It is impossible to remain afloat in water while wearing clothes.
  • Accidents are an inevitable price of technological progress.


Many of the statements are associated with what we commonly call accidents. In fact, every one of the statements is false for specific reasons that we need not go into here. It is sufficient to note that they illustrate common perceptions linked to several types of accident.

Our perceptions of safety are often linked to our perception of the likelihood of an accident happening. But what exactly defines an accident? The word is of such common usage that, surely, we all know its meaning?

Activity 29 (exploratory)

Write down your definition of an 'accident'.


In the Shorter Oxford English Dictionary, I find the definition includes the following key points:


  1. Anything that happens.
    • i.An event; especially an unforeseen contingency; a disaster.
    • ii.Chance, fortune.
    • iii.Medically, An unfavourable symptom.
    • iv.A casual appearance or effect.
  2. That which is present by chance and so non-essential.

These definitions imply an unexpected nature, and certainly we often link an accident to undesirable outcomes, as the references to disaster and unfavourable symptom imply. Indeed, medically we associate accidents with causes of injury or death. However, the reference to fortune implies good luck rather than an unfavourable outcome. So the term is ambiguous and embraces a range of outcomes.

Your answer probably contained at least some of the above concepts.

There are many different ways in which we can define accident, but the key characteristics of any event that could be described as an accident seem to be:

  • the degree of expectedness – the less we expect the event, the more we regard it as an accident
  • the avoidability – the less likely we can avoid the event, the more it is accidental
  • the lack of deliberateness – the less someone is actually involved in causing an event to occur, the more we view it as an accident.

The common linguistic use of the word 'accident' alone gives no indication of causes or of results. When the outcome of an accident is likely to cause substantial damage to either people or property then we often refer to the accident as a disaster. In this context, one academic authority has produced the definition:

An accident is a non-deliberate, unplanned event which may produce undesirable effects, and is preceded by unsafe, avoidable act(s) and/or condition(s).

(Thygerson, 1977)

This definition probably matches our common perception of the word quite well, but let us look at it more closely. 'Non-deliberate' acts include trips and falls, as well as events such as earthquakes. While good engineering design may help prevent the former, engineering can probably only help to minimise the effects of the latter. The 'unplanned' element of the definition can be taken to imply that accidents are inevitable and uncontrollable. Clearly this is not necessarily true, and much engineering practice aims to prevent such events. The phrase 'undesirable effect' raises another problem. Value judgements determine whether something is desirable or undesirable, and so whether a change is required to prevent the 'undesirable effect'. Hence the view on whether something is undesirable may differ from one person to another, may vary with situation, and may differ from culture to culture.

This inconsistency has an impact on the perception of an accident. If someone lights a bonfire alongside a motorway and the smoke blows across the road reducing visibility and causing vehicles to collide, do we regard it as an accident? But what if someone decants petrol in the presence of a naked flame? Was the collapse of the Louisiana levees during Hurricane Katrina an accident?

The above examples have undesirable effects, but are all accidents undesirable? Their outcomes may be beneficial! As children we quickly learn from experience that saucepans on a cooker are hot and cause us pain. So usually we do not touch them again. We can learn from accidents. The discovery of penicillin by Alexander Fleming could be described as an 'accident'.

There is no doubt that engineers learn from accidents because accidents and disasters have often led to changes in design or legislation that improve product or customer safety. Particularly where disasters are concerned there can be a tendency to want to blame accidents on engineering failures. Perhaps you would think that 'good' engineering eliminates accidents, but you can only avoid what you can predict (and as we saw earlier most definitions of an accident would include that it would be unexpected and unavoidable). What engineers can do is design and manufacture artefacts to reduce the likelihood of, and minimise the consequences of, engineering failure. And in this context engineering failure could include both failures of components and failures of systems.