A bad website can generate frustration or anger. It creates a prejudice against the organisation whose brand it carries.

A bad application will die in the marketplace. A bad chair can cripple you. A badly designed car can kill you.

Usability, that combination of design and build that determines whether an appliance, software application or website becomes part of our lives, has often been a neglected part of New Zealand design.

Optimum Usability makes a business out of improving the experience of users.

It's growing fast as New Zealand organisations wise up to the limitations of the No8 wire mentality - the Taranaki gate may be okay for a little-used paddock but it's not what you need outside the milking shed.

Chief executive Trent Mankelow says the field has only taken off in New Zealand in the past decade, and he estimates there are only about 50 or 60 usability experts here.

"We were the first decent-sized usability consultancy when we started in 2003. In Australia, Telstra established a usability team in 1991, so we were far behind," he says.

He believes that as people start looking seriously at usability, things such as websites have improved.

"The quality of web design has improved because of the success of simple sites like Google."

About 70 per cent of his company's work is structuring websites or designing internet applications. It also designs retail stores, interfaces for automatic teller machines, information kiosks, iPhones, in-car navigation systems and even paper forms.

"We're starting to do more of that ... You need to understand the context in which something is used, and try to make sure it's intuitive."

He says the trend to multi-channel and cross-channel service, whereby organisations interact with customers in person and over the phone, email, websites and texting, creates challenges to ensure people get a consistent experience.

"For a long time we were mainly doing user work, but we are moving more to design where we can give more value to customers."

The shift to people accessing the internet on mobile devices and smartphones means website and application designers have to think about usability for a range of platforms. User expectations play a big part. Increasingly, if people see an information screen in a public place they will approach it as if it were a touchscreen - and get a trifle annoyed if they find it needs a keyboard and mouse to access.

In business applications, older users may still look for keyboard shortcuts while younger ones reach for the mouse.

"We will find that more people expect to be able to do swiping and pinching type of gestures.

"Devices are also becoming context aware. They are packed with sensors to measure motion or pressure or location. There's a Nokia phone out which, if you're on a call, will reject another incoming call if you turn it upside down.

"The essence of usability is asking, 'Who are the users, what are their goals, and what is the context of use?' When you find a system that is unusable, the designer has probably not understood the answers to those questions.

"They might understand all the information that needs to be on an immigration form, but they might forget the context - that this might need to be filled in in a dimly lit airline cabin."

Optimum Usability has been thinking a lot about travelling in its work for Air New Zealand. As well as looking at check-in facilities, it also helped design the Skycouch, which allows economy-class passengers to lie flat during flights.

It also worked on Snapper, the electronic ticket system used in Wellington. "We helped them figure out how to improve the on-bus experience. There used to be this annoying message when you tagged on, reminding you to tag off when you left the bus."

The next person on the bus could not swipe their card until the message cleared, causing interruptions to passenger flow. "We ended up replacing the message with a beep when the signal had cleared, and people loved Snapper for it."

The company is also turning its attention to service design, trying to understand why customer service in New Zealand is so bad.

Many of the company's staff are recruited from Europe and the United States. "We find it hard to find qualified New Zealanders. Usability consultants have a range of qualifications - we have cartographers, graphic designers, sociologists, psychologists.

"We're looking for experience and a sense of curiosity and empathy, and the ability to question how people use things and to find how to make them work better."