Designing Error Tolerant Systems

Photo by CHUTTERSNAP on Unsplash

1. Minimize Perceptual Confusions

Controls intended to perform different functions must be made distinct from each other to reduce the chance of users mistakenly using the wrong one. Discernibility can be added in many ways, from using different colors and shapes to spatially separating the controls, making the controls feel different, or even using different control motions. For example, in your car, the stalk behind the steering wheel performs several functions. But, the turn signals are controlled using a different motion than turning on the headlights. This makes it difficult for a driver to mistakenly turn on the headlight instead of the turn signals. However, many of us have mistakenly turned on the wipers instead of the turn signals before, because both functions are executed by the same control motion.

Stalks behind the steering wheel use different control motions for different functions| Photo by Maxime Renard on Unsplash

2. Use system constraints to “lockout” errors

When common error points are known — whether after analyzing a new system or from a preexisting system now being redesigned — certain safeguards against those errors can be implemented. For example, certain applications ask users to perform verification actions once or twice before permanently deleting a file.

Photo by Sigmund on Unsplash

4. Account for multimode systems

In multimode systems, the same control actions often mean different things depending on which mode the system is in. A simple example would be lending an angry tone to an innocuous text by mistakenly sending it in all CAPS. In this case, the user committed a mode error because they forgot that the keyboard was in CAPS Lock mode. The easiest way to avoid these errors would be to not design a multimode system at all, but often this is not possible. For example, it is difficult to design a keyboard without different modes such as CAPS lock, emoji, or symbols. In such cases, what designers can do is to make the indication of a mode change as salient as possible, so the user is cognizant of the fact that the system mode has changed.

Photo by Md Mahdi on Unsplash

Aviation Geek | Grad student — writing to take a break from writing | Making Human Factors accessible one article at a time

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