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UIs and Motorcycles

Let's take a look at a typical gauge that I've removed the units and values from. Ask yourself, which end of the gauge, left or right, marks the low point and which marks the high point.



















In all the straw polls I've conducted the low point is on the left and the high point is on the right. So it would seem the natural expectation is that the gauge moves from left to right as the value being measured (whatever that is) increases and from right to left as it decreases.

So what does this all have to do with motorcycles, I hear you ask. Well, here's a funny story.

I recently bought a new motor scooter:

When I picked it up from the store, I took a quick look as the dashboard and thought, isn't that nice, they've put a full tank of petrol in it for me. Three days later, as I was riding home from work, I started to experience a problem while on the Western Distributor, a multi-lane road, full of peak hour traffic. The engine seemed to be losing power. My first instinct was that I had been sold a dud. I had a quick glance at the dash and realised what was wrong and let the bike slow. A second or two later the engine cut out completely. Thankfully I was in the left lane and I was able to pull over safely. The problem: I had run out of petrol.

Now let's take a close look at that dashboard.

As you can see: the petrol gauge is "back-to-front", ie. the high mark is on the left and the low mark is on the right. Now you may be thinking, well that's pretty obvious. And now that I'm aware of it, I think so too. However, the expectation that it would be the other way round was clearly very strong. My first glance at it and I saw it that way. Now this was almost certainly confirmation bias, coupled with my experience in of all my previous vehicles (2- or 4-wheeled). Look again, the low mark is coloured red. Every time I checked the gauge in those first few days, this did not get through to me.

In the end, there was no harm done. Well, not much, I had to push my bike, on a warm day, 1.6km to the nearest petrol station. However, it could have been a lot worse - losing power at high-speed in traffic is not a safe thing to do after all.

So, I say to all UI designers: follow community and other standards, and do not surprise your users.