Start, stop, smooth

I've just come back from holiday where I was driving a rental Peugeot 308 Eco which had an interesting feature: it automatically cuts the engine when it isn't in use. At traffic lights or junctions the engine simple turns off. At first I thought there was a problem with the car and turned the ignition key to start it again, but after a couple of tries I discovered that it started itself instantly when I pushed in the clutch and engaged a gear.

Timing was essential and for the first couple of days the car and I didn't quite synchronise, resulting in it beeping plaintively at me to push the clutch back in and let the engine start. Once this little dance had been worked out between us it was much smoother than I had expected.

Smoothness is absolutely essential in user interface design and all too many people rushing into the mobile and web app space don't seem to understand this. While Peugeot's engineering team probably didn't think in terms of user experience, they knew that if the eco mode on/off function wasn't blended into normal driving nobody would use it no matter how much fuel it saved.

Another example from the world of cars it the Toyota Prius, which shifts from battery to petrol engine without the driver being aware of the change. Without the animated dashboard display the occupants of the car would be completely unaware of what was powering the vehicle as it is incredibly smooth.

UX designers should reflect on this. Perhaps they are used to using delay-free, lossless local connections. Perhaps they only work on pretty Photoshop comps and don't think about the actual interaction. Whatever it is, it's a pain and will hold up adoption by normal folks.

At a design level, think dynamic from day one and ensure that delays are packed together in natural points. From an engineering point of view, pipeline data downloads while users are reading the last so that their next move is instant. You can almost always predict the most likely action, if they do something other than the obvious next step then they'll expect a delay. Delays break focus and are likely to cause people to click away or sigh and fire up another app that is more responsive.