This uses a couple of gates and two "timers" to simulate a traffic light.
The lower timer is the main one, which controls everything, and the upper one is just in charge of sending I/O to the yellow led. The circuit is meant to be operated with a 9V DC current plus the clocks. I have no idea if this is applicable in real life.
UPDATE
I've tweaked everything and timing works a lot better.
UPDATE //
I added resistors and used 6V LEDs instead. Much better results!
