If you somehow come across an old set of traffic lights, the following tutorial may be of interest. Instructables user "fzumrk" has described how they controlled the mains-rated light bulbs inside the traffic lights with an Arduino and some mains-rated relays. The methods described may not be up to local electrical standards, however it's an interesting read and if you have the lights - food for thought. The results have been demonstrated with a fitting soundtrack in the following video:
A safer method would be with 12V automotive lights, however that's up to the individual. Nevertheless click here for more information. And for more, we're on twitter and Google+, so follow us for news and product updates as well.
If you're working with relays and Arduino - it's much easier to use dedicated relay control boards. Here at Freetronics we have the RELAY4: board, perfect for controlling up to four relays with Arduino (or any other microcontroller's) digital output pins:
Or if you'd like to control up to eight relays - or more at once with an Arduino Uno orcompatible board - consider our RELAY8: board. Controlled via I2C, you can stack up to eight shields with the appropriate power supply to support 64 relays at once: