Working Street Lights In Minecraft With Command Blocks (Tutorial)
(Update) This works for every version of minecraft, unless they update command blocks again...
This is a creative build only, mainly for city builds, and is an easy process you can repeat over and over again. This uses the /clone command, and some minor redstone timing to create lights that change from green to yellow, yellow to red, and red to green.
EthosLab video (Silent Hopper Timer System)
• Minecraft - Tutorial: Hopper Timer