In part I we summarised the unique UX design challenges that apply to POS interfaces and here we summarise the design principles that emerge from the data we gathered through several on-site user research assignments, our lab experiments and the POS designs we created for our customers.
These POS design principles complement the more general UX principles in the design industry by giving guidance on how they can be applied to deliver POS user interfaces that work in real-life.
POS user interface design = ergonomics
This apparent no-brainer hides the difficulty reconciling aesthetics and usability in a POS interface.
The battle between usable and pleasant to look at when designing a POS interface is fierce. Many of the legacy systems look horrifying, but people who got used to them appreciate certain quirks that work as shortcuts. It is critical for designers to know about all these quirks and to understand them; and then to figure out the underlying ergonomics principles so they can apply them in a way that is both contemporary and facilitates the overall aesthetic of the interface.
Throughout our research we have documented many shortcuts and interactions that are truly hideous, but that work. By studying why they are useful to cashiers, we have been able to integrate them in beautiful ways into the contemporary interfaces we have created for POS providers.
Design for hours of use
A POS user interface has to be designed for two very different scenarios: newbies who are confronted with too much information (cashiers come and go), and power users who will execute the same interaction millions of times.
Good luck balancing those tradeoffs…
Designing for a POS interface is sort of like packing for climbing a mountain: anything that seems light on the ground, will feel 10x heavier after half a day of hiking. In a POS interface, every minor inconvenient step in a UX flow, will make thousands of interactions more difficult, every day.
Design patterns are a double-edged sword
Designers of websites or mobile apps can often rely on design patterns to solve usability issues to a mediocre (but sufficient) level. However, in the design of POS interface you can’t get away with that, because. the same design patterns rarely apply to a POS system for reasons outlined in the first part of our series on POS design.
Deciding whether to use a design pattern or not, requires careful balancing of the needs of all stakeholders and of the specific challenges one is trying to solve. Sometimes a design pattern that may seem work will have significant adverse effects in the broader context of the user experience. Designers must understand that POS are used the same way as a standard tablet app and users may end up doing completely different things from what the designer had intended.
Read the Design Guide Part 1: The 16 UX Factors In The Point Of Sale System.
Updates are difficult
Most apps get updated often and even when users feel odd at first, they adapt easily. Providers can iterate and change a lot, going from MVP to a refined product gradually.
But updating a POS interface is more challenging, because after 2–3 weeks of using the interface for hours each day, cashiers become very used to the interface through conditioning. Undoing these automated gestures is difficult and requires conscious override. This introduces a big challenge to cashiers who already have to deal with a lot of other stress factors in their work. Cashiers have to be able to rely on the system without making an added effort to interact with it.
Create order out of chaos
The POS interface has to ensure cashiers are work according to accounting rules and it has to cope with the unpredictable and surprising nature of reality in a retail facility. Often times these imperatives are contradictory and very difficult to reconcile.
The role of the designer is to create a framework where these clashing needs can converge in an interaction that gets the best for all. Coherence and a sound logic beat superficial fixes that only complicate the user experience. Such “fixes” lead to more errors, resulting in a scenario that makes the user’s life difficult and produces erroneous accounting outcomes.
Use visual representation, wisely
Most inexperienced designers would improve a legacy POS software interface by adding product images and icons. However, for each of these a discussion can be had about pros and cons, and there are many.
What’s missing from POS software is not the visual element, but often times it is the understanding of how users achieve outcomes in the daily use of the POS. Therefore, designers have to attend to a deep understanding of the reality first, and add visuals only in the final stages. POS software has to be designed to work in unison with the cashiers mind and visuals are not the shortcut that’s missing.
Create interactions, not buttons
The classical paradigm of POS user interfaces is adding a button for every task. Better to have it in there…
The contemporary trend is about removing buttons and hiding them. However, our user research shows that both of these approaches are wrong because they neglect the reality of how users engage with a POS interface.
Cashiers don’t care about buttons: their existence or lack thereof can be equally problematic. However, cashiers care about meaningful interactions that are finely tuned to how they work.
Design for simplicity, step by step
Tapping is another red herring. Both legacy POS interface and many contemporary POs interface providers got it wrong according to the tests we have performed. Cashiers can be incredibly fast at tapping, as long as interactions make sense. POS ergonomics means understanding the capabilities of cashiers and how they evolve, to design interactions in a way that supports these and to provide fallbacks for the cases where they fail.
Process steps must be designed in a way that balances cognitive load. Legacy systems often have a high cognitive load due to interface with a lot of options and few interaction steps, while most contemporary POS interfaces increase cognitive load due to a labyrinth of steps. Designers must take the best out of both systems to blend simplicity with logic.
The tricky case of customization
Customization can be a great idea, but it can also be a problem. It has to be deployed very mindfully, taking into account that too much customization can lead to problems such as consistency across business points, unhealthy work habits and exploitation of weaknesses to defraud the retailer.
One should be mindful that some people will apply customization where allowed, then disappear from the organization and others will take that customization as a given in the interface. This is how the option to customize the interface may lead down a road where in the long term it reduces the overall level of usability.
Thus customization shall be applied sparingly and only when it fits into the larger user experience paradigm that is emulates the needs of cashiers and the business.
Understand the hardware
Hardware components and their limitations are important in human-computer interaction, but designers of web apps and mobile apps get away with almost anything because the hardware they design for does not offer much room for surprise.
POS systems are different: each provider has a different hardware solution, with display peculiarities and connectivity issues. While most POS providers aspire to offering a universal solution, this cannot be truly reconciled with a proficient user interface, because a POS user interface must include so many tough choices.
Adding “works on any kind of tablet” as a requirement is akin to deciding to have a low value interface that is (hopefully) compensated by more adaptability. This again is a tradeoff that the designer must be aware of.
Lend a helping hand to users
There are very specific processes where users of POS interfaces run into trouble. They result from both the general way of using a POS and from business particularities.
Finding solutions for these key interactions has a significant impact on their daily routine and their wellbeing. It also makes training easier because the biggest part of the training is exercising how to do the difficult things.
Conversely, some tasks are so easy for cashiers that they don’t need more help with.
Looking back over the user studies we have done in real retail locations where we have observed dozens of users, we have discovered many different shortcuts and hacks cashiers use to do their job better.
Many of them have been insightful and inspired original interactions we have created in POS interface designs, but the big picture is this: different users prefer to do things in different ways. Rather than designing a software interface that is rigid and that forces users to do things in a certain way, the interface should be designed in a flexible way, where different people can find different ways of achieving their outcomes.
The healthy dose of validation
The key principle of giving users feedback about the results of their actions applies to POS systems, but designers must approach it in a more nuanced way.
Validations can be tricky because soon enough they may become obsolete and only present a hindrance to the users who would be much faster if they didn’t have to hide messages.
POS software interfaces present a unique set of use cases and of complicating factor. When designing a POS user experience, the general principles of human-computer interaction must be augmented by these additional principles that add nuance to the design process.
The principles we have outlined arise out of numerous user studies we have performed on cashiers in real retail location, lab test on current POS systems and our own work in designing for POS providers.
If you are interested in more UX case studies, check out The Border Force Goes Digital on our website, https://www.interface-design.co.uk/.
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