Delhi Metro most comfortable
Says IIT study using vibration levels inside trains as measure of comfort Commuters delight: Vibration levels inside Metro trains meet the "most comfortable' tag of ISO standards. NEW DELHI: The Delhi metro railway is one of the most comfortable means of public transport, according a study conducted by the Indian Institute of Technology, Delhi, using equipment developed in the United Kingdom. The study used vibration levels experienced by passengers in the metro as a measure of the comfort level and compared it with international standard ISO 2631-4-1997.