Usability Heuristics in Critical Systems — #4 Consistency and Standards
Learn more about the importance of standards and consistency in successful UxD.
In our last article about Jakob Nielsen’s heuristic and critical systems, we discussed the importance of user control and freedom — the importance of allowing users to undo and redo an action or task.
This time, we’ll focus on the fourth heuristic, consistency and standards, and gain a better understanding of why we should think about them when designing products.
#4 Consistency and standards
Consistency, n.: the quality of always behaving or performing in a similar way, or of always happening in a similar way.
Standards, n., pl.: something established by authority, custom or by general consent as a model or example.
Systems should follow these two concepts and not, as is sometimes said, reinvent the wheel. This way, they will be easy to learn and use, and the user experience will be improved.
Why?
When products adhere to standards, users know what to expect. They know how to interact with them and feel much more confident about using them. Users should not have to wonder whether different words, situations or actions mean the same thing. Eliminating confusion and making things easier to understand will lead users to their end goal with minimum effort.
How?
1. Follow standard patterns and platform conventions.
2. Keep UI (user interface) and terminology consistent across the product (and multiple platforms) by creating a design system.
3.Meet user expectations with consistent interactions.
Everyday life examples
It is an established norm that, if the yellow light on the left side of the car is flashing, it means that the car will turn to the left. Likewise, if the yellow light on the right-hand side is flashing, we can assume the car will turn right. Now suppose that a new car model comes up, and this model doesn’t follow the standard — what would happen? Will road users immediately understand what is going on, or will it cause trouble on the roads? And in the middle of all this, would people’s lives be at risk?
Breaking convention
We can break convention but only if it’s absolutely necessary to the task or if we can be sure it will improve efficiency.
Generally, when a warning system breaks, a flashing red indicator is used to alert the user that there is a problem. We are used to this pattern; the flashing light gets our attention. But sometimes we do have to break this convention.
For example, take the spacecraft used in the Apollo lunar missions, which did just the opposite. Their warning lights remained illuminated when everything was fine and turned off when there was a problem. This stopped the astronauts from missing a potentially fatal system error in case of some of the warning lights burned out during the journey. Whatever the situation, if the system crashes, it must be detectable. To make this kind of decision, we must focus on the user’s needs, their context and their tasks.
Consistency and standards for critical systems
Intro
On 8th January 1989, British Midlands Flight 92 crashed onto a nearby motorway in Leicestershire, whilst attempting to make an emergency landing at East Midlands Airport. Of the 146 passengers and crew on board, 47 lost their lives and 74 sustained serious injuries.
The problem?
The model of the airplane was new, so one would assume that the technology was as up-to-date as possible.
So, what happened? Vibration levels in the left and right engines could have helped the pilots determine which engine had suffered damage and shut it off. This information was displayed at the interface — the technology was there, so why did the pilots miss this engine fault? The problem was that the user interface showing the levels of vibration was not consistent with previous designs; the dial needles were changed to easily- missed dotted lines located on the outside of the dials.
What happened?
The pilots didn’t see that the vibration levels had reached their maximum. This kind of information should have been displayed in a way that couldn’t be missed or misinterpreted. And the context of use should be always present when designing critical systems. The airplane was shaking violently, and the cabin was filled with smoke; the pilots couldn’t have been expected to scan the whole interface searching for clues.
Final thoughts
Users should be able to use several different websites, applications, and products without any major effort. They carry with them a set of expectations from one product to another. This is something designers should always take into consideration, ensuring users ‘get their way’ and avoiding any undue confusion.
“Don’t forget that people spend 90% of their time interacting with other apps.”
Consistency is a simple concept, but it’s not always easy to apply. There will be some situations in which too much consistency, or consistency across the wrong elements, will confuse users even more than the lack of it.
In the case of cross-platform systems, we should always use consistent UI and terminology, but with the interactions we may have to make some distinctions. The same interaction on a mobile phone and on a platform with physical controls may not make sense. Let’s think about a thermostat. If one thermostat used a physical slider to control the temperature, another with a touch screen could use two up and down controls which may be simpler and more precise.
Focus on achieving consistency across devices and follow standard patterns and platform conventions. This approach can help users in their tasks and smoothen the learning curve. In critical systems, it could even mean the difference between life and death.
Get in touch
Sara Carvalho, User Experience Designer at Critical Software
Designing for critical systems
uxd@criticalsoftware.com
