Summary

The traffic light is fixed on a base, which is closed by a lid. A 9 volt battery, eventual electroniscs and an on/off switch find a place in the base.
In the video, the leds are activated by ATtiny85, programmed with Arduino.
If electronics is not your thing, just take a three position switch and use manual control to regulate the traffic.
https://youtu.be/0fCmEhM0ciU