Question: according to dot what is the most common mode of transportation for hazardous materials
[{'answer': 'truck', 'provenance': [{'wikipedia_id': '38688637', 'title': 'Hazardous Materials Transportation Act', 'start_paragraph_id': 16, 'start_character': 160, 'end_paragraph_id': 16, 'end_character': 165, 'bleu_score': 1.0, 'section': 'Section::::Background.:Importance.\n'}]}, {'provenance': [{'wikipedia_id': '38688637', 'title': 'Hazardous Materials Transportation Act', 'start_paragraph_id': 16, 'start_character': 0, 'end_paragraph_id': 16, 'end_character': 959, 'bleu_score': 0.9613050207098811, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12461824593280995433}, 'section': 'Section::::Background.:Importance.\n'}]}]