How long will it take?

When talking about user experience, predictability is good. Some of the things we interact with in our daily life, though, are lacking from this perspective. Consider traffic lights: they are among the most widely diffused devices and they can’t be simpler. Green: go. Red: don’t. Yet, they are widely recognized as universal sources of frustration. Red lights, in particular, are able to annoy almost anyone. And that’s not just because they are inevitably perceived as something meant to slow you down, but also because they leave you almost clueless about when they’ll eventually turn green.