Question: when were traffic lights first used in the uk
[{'answer': '9 December 1868', 'provenance': [{'wikipedia_id': '163395', 'title': 'Traffic light', 'start_paragraph_id': 12, 'start_character': 3, 'end_paragraph_id': 12, 'end_character': 18, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}, {'provenance': [{'wikipedia_id': '163395', 'title': 'Traffic light', 'start_paragraph_id': 12, 'start_character': 0, 'end_paragraph_id': 12, 'end_character': 1194, 'bleu_score': 0.94069184802309, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7676175179400024000}, 'section': 'Section::::History.\n'}]}]