How to create a Scratch program for two traffic lights at an intersection.
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Basic traffic light in Scratch:
https://youtu.be/R4aNgFjxstE
Creating a traffic light that sends a 'stop' broadcast to a robot in Scratch:
https://youtu.be/4mqFnU93TFs
How to create a Level (train) Crossing in Scratch:
https://youtu.be/i7oTEsGmTQQ