As an experiment in being a cheapskate (I normally spend too much), I travelled on a Megabus from Winchester to London at the weekend. To pass the time, I attempted to assess the usability of the light situated outside the toilet (I’d left all my good CDs at home). My train of thought was as follows:
After seeing the light turn on when someone went inside, I assumed I was correct in my initial guess - it was to indicate it was occupied. So far, so good - although things would have been less certain if you hadn’t been sitting next to it and seen it do this before. However, the light stayed on for 3 minutes after someone left the toilet. After seeing this consistently happen twice, I figured it must be going through some cleaning cycle - thus the light really meant ‘do not enter’ rather than ‘occupied’. I was just congratulating myself on figuring out this rather straightforward pattern when a further complication arose - as we approached London, and the roads got bumpier (or so I theorized), the light seemed to switch on and off fairly randomly, and this time I just couldn’t correlate it with anything meaningful. Perhaps just a faulty connection in a switch somewhere, but it made me question my previous two conclusions to the extent that as I got off the bus, I realized that I hadn’t really learnt anything at all. Perhaps the light had nothing to do with the toilet, apart from being located nearby.
This is a trivial example, and you could argue it didn’t matter. But also, after spending over 2 hours studying the light, and still not being 100% sure what it did, I couldn’t help but think that maybe, just maybe, it could have been designed to be more obvious (or at least have the faulty switch fixed). These little technological irritations don’t _normally _hurt anyone (although there have been plenty of similar examples that have caused ‘pilot error’ plane crashes, for example), but they are still things that us technologists should aim to understand and defeat, if only for the sanity of ourselves and those around us.
For a lot more discussion on this topic, see Don Norman’s classic book The Design of Everyday Things.