This chart illustrates that similarity attributes should be considered with respect to the operational situation :

• In routine operation, perception should be based on distinctiveness of the feature representation on screen, so that they are recognized at a glance.
• In exceptional situations ( under hazard ), uniformity should be preferred, when it is assumed that the operators are not familiar with the feature representation.
• For the same reason, uniformity is also best for unpredictable situation ( under threat ).

Updated on 19 Mar 2017.