You may have seen my video of my PiStops in action, but if not, it is here on the right:)
The PiStop is a simple traffic light add-on for the Raspberry Pi, and is so simple that you can program it in scratch! (Like the video on the right). The traffic lights can be plugged directly on to the GPIO pins of the Pi, and require no soldering or setting up!
Full instructions on how to use the PiStops can be found here. Oh yeah, and they only cost £2.95 each!!