Question: what are the various planned maintenance schedules that are generally used
[{'answer': 'date - based', 'provenance': [{'wikipedia_id': '91191', 'title': 'Maintenance (technical)', 'start_paragraph_id': 39, 'start_character': 46, 'end_paragraph_id': 39, 'end_character': 57, 'bleu_score': 1.0, 'section': 'Section::::Types.:Preventive maintenance.:Planned maintenance.\n'}]}, {'answer': 'based on equipment running hours', 'provenance': [{'wikipedia_id': '91191', 'title': 'Maintenance (technical)', 'start_paragraph_id': 39, 'start_character': 58, 'end_paragraph_id': 39, 'end_character': 90, 'bleu_score': 1.0, 'section': 'Section::::Types.:Preventive maintenance.:Planned maintenance.\n'}]}, {'answer': 'distance travelled by the vehicle'}]