Google interview question: How to design elevator interface?

I read online that Google asks people how they would design an elevator interface for a 900 floor building in the technical interview. I’m stumped. How would I start?

Think about the what, who, why, how, and where. This question can trap junior candidates, who are more likely to jump into the design too quickly.

You need to begin by identifying your user and breaking down your assumptions. You are probably thinking that the elevator is for people, but what if it needs to be designed for zoo animals, cars, or something else? Is the building residential or non-residential? Consider socioeconomic factors. Is this an elevator for a luxury building? Or are you on a tight budget?

In terms of usability, you want to consider that the elevator interface may be used by multiple age groups, possibly including children, adults, and the elderly. What kind of emergency evacuation features do you need to add? Can the interface be used to call 911 or building security? Are there resources for people who are blind or deaf? For example, you might consider adding braille or an interactive voice response system. Is the interface available in multiple languages?

While you should definitely focus on ergonomics and safety, you also need to think about what will drive contracting companies to select your elevator design. Is the elevator interface intuitive and aesthetically pleasing? Does the elevator link with an app? Will you need a fob? Can the doorman control the elevator from a distance?

As you brainstorm, make sure that you are thinking about implementation. How do you correlate needs to features? Never brainstorm for brainstorming’s sake. Rather, your questions should help you create a vision for the product. Each question should identify a need, which in turn will give you an idea for one of the product’s features.