I don't know why this never occurred to me before, but today on Twitter, several people who are attending the 2011 Accessibility Summit pointed out that traffic lights aren't, traditionally, accessible. Think about it. If you're colorblind, does red, yellow, green tell you as much information as you need, as easily and quickly as you need to know it?

Turns out, some Canadian provinces deal with this by adding shapes to the lights, as well as colors. This is an example from Halifax, Nova Scotia. Thanks to Seth Meranda for linking it!

Image: Sprocket at en.wikipedia. Used via CC.