When usability (or lack of it) can kill

Some of my colleagues in the UX community cannot do so much as walk out their front door without seeing some interesting application of technology 'in the wild' that compels them whip out their camera, post photos online, tweet and blog on the subject. But not me, no sirree. Or at least, not until now.

Now I'm as interested as the next nerd in the contextual elements of technology, the way in which society co-opts it, makes it work (or not as the case may be) and new uses emerge to meet unforeseen requirements. It's just that, well - when it's a choice of stopping for two minutes and fumbling for the camera application on the greasily unresponsive screen of my iPhone to take a photo of some interesting technological phenomenon, or simply continuing on my way, trying to be not so late to work is usually the winner.

Except this one really makes me angry. I mean, not annoys me, so I'll rant about it ad infinitum all day. Not angers me to the extent that I might even post a sarcastic line on Twitter about it. No, this one fills me with righteous anger.

In the surburb of North London I call home, the local council have installed new pedestrian crossing lights in the high street. Not the old kind, but a new formula I've not seen before. Observe, what's wrong with this picture?

That's right, when you face the other side of the street there are no lights telling you to cross or stay where you are. The damn thing is on your right on your side of the street.


Let's consider mental models for a moment - how have generations of local people (target users) learnt to cross the street?


(1) Walk up to the crossing, press the button on the unit on your right hand side.

(2) Face the set of lights on the other side of the road

(3) Wait for the lights opposite to display the 'green man' symbol, then cross

What happens now? Well I'll tell you -

(1) Walk up to the crossing, press the button on the unit on your right hand side.

(2) Face the set of lights on the other side of the road

(3) Begin to wonder why the traffic has stopped, but there is no green man displayed

(4) Shake your head at the foolish people crossing before the green man is displayed

(5) See that something green appears, automatically start crossing before you realise that it is, in fact the green light telling oncoming traffic to proceed

(6) Collide with oncoming vehicle, sustain terrible injuries

This isn't just a personal problem I have with this death trap system. The research demonstrating how users apply existing mental models to new systems, and the problems caused by the resulting mismatched, automatic behaviour are well documented.

Now, part of the reason why I don't bother publishing my views on every instance of bad design I encounter in life, is that life is well - simply too short. The other reason however, is that if you are a company losing money because you cannot get your head around the relatively simple idea of user-centred design and testing with real users, then you deserve everything you get.

But when you design safety-critical systems such as pedestrian crossings, you have a moral obligation to do something. Experiments in design should never be inflicted on the public in this way.

Eventually, I suspect these lights will be replaced. I just wonder if it will be due to the advice of a human factors specialist, or will it be when the body count starts to rise, and local councils start getting sued?