So far we have considered the problems of poor ID in terms of the loss of productivity and efficiency to business. There is another important aspect to consider: the issue of safety, both for the user of interactive products and for the general public. Safety can be severely compromised by poor ID, with potentially serious consequences.

Systems in which human or environmental safety is of paramount concern include cars, aircraft, air traffic control consoles, nuclear power plants, control systems and medical devices. TheDaythePhonesStopped (Lee, 1992) provides scare stories demonstrating the importance of ID for safety-critical systems. Box 4 gives a few snippets taken from this book. The examples in Box 4 should have convinced you of the importance of good ID. But if you have found it difficult to relate to these 'catastrophic' examples, there are many less disastrous but stillproblematic examples that may be more familiar to you. For example, when I am driving in fog it can take me a few moments to locate my car's fog light button, because I only use it occasionally and it is partially obscured by the steering wheel. During these moments I am distracted, and this could result in an accident.

Now read the article in Box 5. This article was written by Don Norman, a cognitive psychologist and leading ID expert. He originated many of the concepts in this unit. I have included the article here because it addressesani mportants afety-related applicationdomainwithwhich you will probably be familiar. I hope this reading will demonstrate to you the importance of the issues contained in M364 in an accessible manner. Whilst reading this you should recall that designing the user interfaceis an aspectofID.