dug 
Franco just sent me this utterly wonderful example of what happens when design is divorced from context-of-use:
It turns out, perhaps in an homage to bad engineering everywhere, that the inefficiency of incandescent light bulbs was previously relied upon to keep traffic signals unimpeded.
Also, there is just something so ‘human factors’, so deliciously broken about humans relying on what is–on paper–a defect to support their activity. It reminds me we should never assume we fully understand a system, and we certainly shouldn’t be afraid to claim that without testing, we can’t be sure.
Score +1 for user-centred-design:-)