According to an article today in the San Francisco Chronicle, Pleasanton California's traffic engineers have created a traffic signal with a bad attitude. It senses when a speeder is approaching and immediately turns from green to yellow to red.
This isn't a joke, when driver's approach the light the will see an electronic sign that gives the speed limit and then flashes their actual speed. If that speed is too high the light ahead turns red forcing them to come to a full stop. I'm debating the implications here, but my first sense after reading the article (and checking that the date wasn't April 1st) is that this would be a good thing.