Usability - simple, obvious and timely
I recently bought a recent second hand car, and was struck by how simple innovations can continue to be made in terms of usability. You'd think that pretty much all sensible ideas about making the driving experience easier had been thought out years ago for cars, but it's not so.
How often have you jumped in a car, particularly a rental one or a friend's, and gone to fill up with petrol at the service station, only to do the petrol cap dance? (That's the one where you park the car, only to discover the petrol cap is on the wrong side from the bowser, so you see if the hose will reach, or just accept that you have to 3-point turn the car to face the other way.) Or spend time wondering as you're approaching the service station which side it's on, and trying to peer into the rear view mirrors to see if you can see the line of the flap in the car body? (Instead of focusing on the road ahead.) I've discovered an ingenious mechanism where (if you have a remote release) you can pop the flap and see which side it's sticking out on in the mirrors which is a bit easier. But not all cars have remote releases either, and you have to be driving slowly else the wind will keep it pressed in.
The car, a Subaru Impreza, solves all these problems at a stroke.
The solution: two words "Fuel door" (simple) and an arrow (>) to indicate the side it's on (obvious).
These are positioned right above the fuel gauge, so when it's heading towards empty and you're thinking about visiting a service station, the information you need is right there in your face (timely).
Of course, cars are far more simple to consider from a usability perspective than stupendously complex and constantly changing software systems. But the principles remain the same. I believe usability, when boiled down to an essence, is all about making every aspect of a (software) system that a user has to interact with:
- Simple - so that anyone can understand.
- Obvious - so that it's clear what action to take.
- Timely - so that the information is available when you need it.
For more reading, Peter Merholz's writes eloquently about the first two aspects - simplicity (in Explicit design's relationship to simplicity), and obviousness (he uses the term explicit, in Explicit labels).
I've struggled a bit to find people writing about timeliness of information with respect to usability, especially in software systems. Even my favourite book of all time on design (Donald Norman's The design of everyday things) doesn't approach this explicitly. Norman does discuss the issue implicitly, using the concepts of knowledge in the world and knowledge in the mind. He writes,
Knowledge in the mind is ephemeral: here now, gone later. We can't count on something being present in mind at any particular time, unless it is triggered by some external event or unless we deliberately keep it in mind through constant repetition (which then prevents us having other conscious thoughts). Out of sight, out of mind. [p. 80]
In the car example above, ultimately knowing that the petrol cap is on the right may move to being knowledge in my mind. Reassuringly for me, it can stay as knowledge in the world, and is there to remind me every time I need it.