The correct option is
B Not
Options A, B and D: The passage describes "a great confusion" at the traffic jam. This would be possible if the lights were NOT working. If they were 'still working', or 'yet working', then there wouldn't be any confusion, and the traffic would move smoothly.
Hence the correct option is B 'not', and A and D are wrong.
Option C: 'On' refers to the top or surface of something. It does not relate to the given sentence.
Hence option C is incorrect.