“…1. While these hoses are very important to maintain ordinary service of trains, it is difficult for current air hoses, which are made of natural rubber layers and cotton fabric layer, to serve safely and reliably for longer period of time than the current exchanging period (generally four years at JR companies) because their materials do not have enough durability against sunshine (ultraviolet ray), heat and shock from the stroke of hard particles such as ballast 1), 2) . It requires much labor to exchange current air hoses every four years.…”