The Two Faces of Safety
safety has a negative and a positive aspect, though it is mainly the former that claims attention. They are summarised below:
- • The negative face is revealed by reactive outcome measures: accidents, fatalities, injuries, loss of assets, environmental damage, patient safety incidents and adverse events of all kinds. Then there are also close calls, near misses and 'free lessons'. All of these are readily quantified and hence much preferred by number-hungry technical managers. These numbers may be convenient and easy to manipulate, but beyond a certain point, they have very dubious validity, as we shall see later.
- • The positive face of safety relates to the system's intrinsic resistance to its operational hazards. It is assessed by proactive process measures - indices that reflect an organisation's 'health' both in regard to production and safety. I will say more about these indices later.
The main purpose of the 'safety space' model is to elucidate what exactly is meant by the positive face of safety. But before describing it, let me sneak in yet another metaphor that illustrates the notions of vulnerability and resilience. Figure 14.1 shows a ball-bearing (representing the system) sitting on top of variously shaped metal blocks. Both the ball-bearing and the block are subject to continual jigglings or perturbations that seek to topple the ball-bearing off the block - equivalent to an accident.
Figure 14.1 Illustrating vulnerability and resistance. The arrows at the top of the figure represent perturbing forces
It is clear that the top ball-and-block are the most vulnerable (easily toppled), while the bottom set are the most resistant. Note, however, that even in this bottom configuration, it is still possible to dislodge the ball. If you prefer a more homely example, think of a tray with an egg and a Pyrex bowl on it. In the vulnerable arrangement, the bowl is inverted and the egg is on top. In the resistant arrangement, the egg is inside the bowl. Perturbations come from tiltings of the tray.