confusing, however, since in everyday language the words ‘risk’ and ‘hazard’ are used interchangeably (see, e.g., the definitions of these words given in the Oxford English Dictionary).
accidents at work—probably the overwhelming majority. The contribution may very well be a decisive one, in that but for the error in question the accident would not have occurred. Errors do not arise in isolation, however. Their occurrence is very often contingent upon other adverse circumstances or features of the working system that lie outside the jurisdiction and control of the person concerned.
Psychologists of the cognitive persuasion have made a number of attempts at classifying human error, doubtless to their own satisfaction. For practical purposes it is important to recognize two particular categories:
§ errors of judgement in the appraisal of risk;
§ errors of execution in the performance of the working task.
True errors of judgement in the appraisal of risk stand at one end of an unbroken continuum which stretches through violations of safe working practice (having greater or lesser degrees of conscious intent) to the deliberate and premeditated criminal act (of vandalism, sabotage, assault, etc.). Errors arising in task performance are commonly system-induced, in that there may be deficiencies in the design of the working system (most typically at the operator/machine interface) which make the person’s working task more difficult and thus render him more error-prone.
Notwithstanding that this may be so, however, such errors may also have an attitudinal component, in that by the investment of additional care and effort (conscious or otherwise) it may in some cases be possible for the person to adapt to (and cope with) the deficiencies of the system. So looked at from another standpoint, the system-induced performance error may be construed as stemming from a want of attention, etc.
In English law, a crime has two components: the criminal act (actus rea) and the criminal intent (mens rea). The law recognizes the existence of an important grey area, between the true error (for which no blame accrues) and the premeditated criminal act. This recognition forms the basis for the concept of negligence: the failure to act with a reasonable degree of caution or prudence in the face of a risk that is foreseeable ‘in reasonable contemplation’.
At law, an injury may stem from a ‘true accident’ (for which no one is to blame); it may stem from the negligence of a single party (e.g. either the employer or the employee); or it may be attributable, in various measures, to the negligence of two or more parties. Thus the outcome of a personal injury claim might, for example, be that the losses arising from that injury were attributable principally to the negligence of the employer (in failing to institute a safe system of work); but that there was also a significant element of ‘contributory negligence’ on the part of the employee (in failing to take reasonable care for his own safety). The damages awarded would be adjusted accordingly—on the basis of the court’s estimate of the relative magnitude of the two causative contributions. In other words, theories A and B of accident causation would both apply in part.
8.1.1 The catastrophic failure of complex systems
When an accident has particularly serious consequences (e.g., multiple loss of life or large-scale environmental contamination), we are likely to refer to it as a ‘disaster’ or a ‘catastrophe’. I have dealt at length elsewhere with the role of human error in the catastrophic failure of large-scale human-made systems—nuclear incidents, plane
crashes, etc. (Pheasant 1988a, 1988b, 1991a). For present purposes we shall limit ourselves to just one example, the loss of the Herald of Free Enterprise, which illustrates the main points at issue particularly well.
The reader will recall that on 6 March 1989, the cross-Channel car ferry Herald of Free Enterprise put to sea from Zeebrugge with her bow doors open. An inrush of water flooded the large unobstructed spaces of her lower car deck, causing her to capsize, and 188 lives were lost. The direct responsibility for ensuring that the bow doors were closed lay with the Second Mate who, as it transpired, was asleep in his cabin (where he remained until he was awakened by the ship rolling over). The overall responsibility for the safety of the ship lay with the Captain, who was in his normal place on the bridge. From a human factors standpoint the most striking feature of the accident was that from his customary position on the bridge, the Captain had no direct means of knowing whether the bow doors were open or not. There was no visual display—such as a simple warning light, for example—to provide him with this critical information. Neither was it anyone’s particular duty to tell him (although this latter point remains surrounded by a certain air of vagueness). The Captain’s fatal decision to put to sea may thus be construed as a classic system-induced error.
A number of other adverse circumstances were contributory factors. The tide that day was particularly high, making the loading of the ship difficult (particularly since
Figure 8.3 The Zeebrugge-Harrisburg syndrome (New Scientist, 21 January, 55–58 from S.Pheasant, 1988)
the ramp at Zeebrugge had been designed for a different type of vessel); because of the fierce economic competition of the cross-Channel ferry routes, the crew were under considerable pressure to achieve the fastest possible turnaround time in port;
because of vandalism, life jackets were stored in inaccessible lockers; and so on.
The relationship between these various contributory factors, in the chain of causation which led to the catastrophe, are summarized in Figure 8.3. I have referred to this overall process as the Zeebrugge-Harrisburg Syndrome. (The reader will recall that the ill-fated Three Mile Island nuclear reactor was in Harrisburg, Pennsylvania.)
It became apparent at the subsequent Court of Inquiry that it was by no means unknown for ferries of this type to go to sea with their bow doors open. Other captains had commented on the problem and the suggestion that warning lights should be installed had been passed up to the board level of the ferry company. The suggestion met with derision. The honourable Mr Justice Sheen concluded that
‘from top to bottom the body corporate was infected with the disease of sloppiness’. The Captain, the First Officer and the Second Mate were found to be negligent. The Captain lost his operating certificate for one year and the First Officer for two years.
The episode has two interesting legal postscripts. The Captain appealed against the loss of his certificate on the grounds that going to sea with the bow doors open was a common practice. The appeal failed on the grounds that the fact that a particular form of negligence was rife in the world of car ferries did not condone it in any individual case. This finding is in some measure unusual in that the defence of ‘normal custom and practice’ is often successful in personal injury claims. An attempt to bring a criminal prosecution against the ferry operators for ‘corporate manslaughter’ also failed, it being ruled that the risks attendant on going to sea with the bow doors open were not sufficiently obvious to warrant such a charge. The common-law test of
‘reasonable foreseeability’ does not apply here, the criterion applied in the criminal charge of manslaughter being a more demanding one. The risk would have to ‘stare you in the face’.
8.1.2 Everyday accidents
We now return to the everyday accidents of the shop floor as categorized in Table 8.1. Each category of these presents its own set of ergonomics or ‘human factors’
issues.
Slipping, tripping, and falling accidents (for example) very often result from a lack of ‘good housekeeping’—the failure to mop up spillages, keep walkways free from obstructions, trailing cables, and so on. This stems in turn from a defective safety culture and ‘the disease of sloppiness’. Issues of environmental design may also be involved, however, for example the layout and lighting of the working area, the slip resistance of flooring materials, etc. This author continues to be amazed by the unsuitability of the flooring materials used in public buildings—especially around entrances, etc., where in bad weather the floor can get muddy and wet faster than staff can be reasonably expected to keep it clean and dry.
Contact with machinery accidents remain a common cause of serious injury at work. The safeguarding of machinery raises some interesting points in the theory of anthropometrics. The concept of a safety distance is based upon a reversal of the normal criteria of reach and clearance. A safety guard or barrier will fulfil its
function of separating people from the hazardous parts of machines, either if apertures in the guard are sufficiently small to prevent access by a particular body part (finger, hand, arm, etc.), or if the distance between the aperture and the hazard is sufficiently great for the latter to be out of reach (by the body part in question).
The limiting user is thus one with a small finger (hand, arm, etc.) in the case of aperture size and a long finger (hand, arm, etc.) in the case of the distance. (In theory we also need to allow for the correlation between the length and girth of the body parts in question; but in practice this is likely to be small and if we assume it to be zero we will err on the side of caution.) Safety distances are the subject of a series of British and European Standards to which the reader is referred for further information.
Regrettably it is all too common for people to seek ways of ‘defeating’ the safety mechanisms of machinery in the interests of increased output—and for serious or fatal injury to result. There have been prosecutions under the UK Health and Safety at Work Act for fatalities caused in this way.
The reader will thus note that for both the classes of accident discussed above, theories A and B are both applicable to some extent as to accident causation. Overall, this is true for most other classes of accident too—up to and including the catastrophic failure of complex human-made systems.
We note also the very general applicability of ‘the ergonomic approach’ to accident prevention. We turn now to a large and important class of work injuries in which ergonomic issues are of decisive causative significance and in which theory B will in general be very much more applicable than theory A.