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Visibility and audibility of safety-critical functions

This pattern serves as a guideline for the display of safety-relevant functions.


Information considered safety-relevant is not displayed, or is covered by other user interface components, or an audible alarm cannot be heard, or can be mixed up with similar alarms.


This pattern adds an additional design constraint. A possible consequence is to avoid dialogs cover up safety-relevant parts of the interface.


The solution describes guidelines for the design of user interface components and audible signals.

Safety impact

Using this pattern consistently reduces the probability of errors caused by misreading screen displays or even missing important events.

Usability impact

This pattern increases avoids misinterpretations when reading the screen, and therefore, reduces error probability.


Has been used in several European railways voice communication devices.

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