Question: when was the first manual traffic signal invented
[{'answer': '1868', 'provenance': [{'wikipedia_id': '163395', 'title': 'Traffic light', 'start_paragraph_id': 2, 'start_character': 123, 'end_paragraph_id': 2, 'end_character': 127, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '163395', 'title': 'Traffic light', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 440, 'bleu_score': 0.972782728923768, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8648237245578377640}, 'section': 'Section::::Abstract.'}]}]