Tolerance for Error
Tolerance for error means that products should be designed so that their most important features are easiest for people to reach. In contrast, parts of a product that create hazards should be either removed or limited as much as possible. For example, blade guards on knives or other sharp tools help people use them safely and avoid injury. Since knife handles are safe at all times, they do not need to be covered. On the other hand, people keep blades guarded, or store them in knife blocks. People only expose a knife blade when they are about to use it.
Moreover, products should warn their users about hazards or errors. For instance, labels on medicine bottles or other packaging explain dosages and side effects. These labels warn people about the amount of medicine they should safely swallow, so that they avoid the error of taking too much. Likewise, labels state the side effects, or possible hazards, people encounter no matter how much medicine they take.
Similarly, products should include failsafe features. For example, kettles that automatically turn off after the water is boiled prevent people from making errors such as forgetting to turn the kettle off.
Finally, products should lower the risk of unconscious action during tasks requiring focus. For instance, our laws prohibit texting and driving because drivers need to focus on their surroundings and safety. When drivers pay attention to their phones, they grow distracted, and fail to notice dangers on the road. As a result, laws against texting and driving prohibit people from focusing on their phones when they need to keep their attention on the task at hand.