Number of words – 397 In commercial installations, the pressure to keep systems running is immense. Considerable money might be lost if an expensive system is shut down. Operators are often under pressure not to do this. The result has at times been tragic. Nuclear power plants are kept running longer than is safe. Airplanes … Read more

Number of words – 366 Some rules come from experience; others are formal procedures in manuals or rulebooks, or even less formal guides, such as cookbooks for food preparation. In either case, all we must do is identify the situation, select the proper rule, and then follow it. When driving, behavior follows well-learned rules. Is … Read more

Number of words – 240 An accident with an Airbus airplane illustrates the problem. The flight control equipment (often referred to as the automatic pilot) had two modes, one for controlling vertical speed, the other for controlling the flight path’s angle of descent. In one case, when the pilots were attempting to land, the pilots … Read more

Number of words – 192 The immediate cause of most memory-lapse failures is interruptions, events that intervene between the time an action is decided upon and the time it is completed. Quite often the interference comes from the machines we are using: the many steps required between the start and finish of the operations can … Read more

Number fo words – 516 Error occurs for many reasons. The most common is in the nature of the tasks and procedures that require people to behave in unnatural ways—staying alert for hours at a time, providing precise, accurate control specifications, all the while multitasking, doing several things at once, and subjected to multiple interfering … Read more

Number of words – 491 Sometimes everything that is needed cannot be made visible. Enter sound: sound can provide information available in no other way. Sound can tell us that things are working properly or that they need maintenance or repair. It can even save us from accidents. Consider the information provided by: • The … Read more

Number of words – 176 On most subway trains, the doors open automatically at each station. Not so in Paris. I watched someone on the Paris Métro try to get off the train and fail. When the train came to his station, he got up and stood patiently in front of the door, waiting for … Read more

Number of words – 1,213 I was in Asia, giving a talk. My computer was connected to a projector and I was given a remote controller for advancing through the illustrations for my talk. This one had two buttons, one above the other. The title was already displayed on the screen, so when I started, … Read more

Number of words – 136 Usability is not often thought about during the purchasing process. Unless you actually test a number of units in a realistic environment, doing typical tasks, you are not likely to notice the ease or difficulty of use. If you just look at something, it appears straightforward enough, and the array … Read more