Ever wondered what the inside of those little 'WAIT' switches at road crossings looks like? Well here's the answer, courtesy of some asbo-baiting local ruffian (and some poor photography from yours truly):

Yes, it is two wires connected to an ordinary household 40 watt bulb, and yes, it is exactly the same circuit you made in Science class when you were about 9. Doesn't the world suddenly seem a much simpler place?