The buses are prepared during the Daihaseisai as a means to relieve the overcrowded trains and subways. Moreover, due to the degree of overcrowding, they are used because there aren't enough human drivers for the regular buses. Since the Board of Directors have prohibited by travel by car as part of their plans to deal with all the visitors, the buses are able to move readily in the streets despite the busy event. During the Daihaseisai of the current year of the story timeline, 70% of the buses that were used for the event were automated.