Here's an interesting take on road design from dutch traffic engineer Hans Monderman (from Roads Gone Wild in Wired, December 2004):
"The trouble with traffic engineers is that when there's a problem with a road, they always try to add something," Monderman says. "To my mind, it's much better to remove things."
Gotta love that thinking.
"[...]the cars look out for the cyclists, the cyclists look out for the pedestrians, and everyone looks out for each other. You can't expect traffic signs and street markings to encourage that sort of behaviour. You have to build it into the design of the road."
That's exactly right. Street signs don't encourage at all. They dictate. Do this, don't do that. Do it any other way, and you'll be breaking the law. And they can give a false sense of security - the more explicit rules there are, the more people tend to rely on everyone following those rules. That inevitably leads to unawareness and, in the long run, accidents that could have been avoided if people had just looked around instead of blindly staring at that red light, waiting gor it to turn green.
Oh, and I am so putting traffic engineer/road designer on my list of backup careers.