My hometown, Beijing, has the most advanced(先进的) subway system in China. I like to travel by subway,   because it brings a lot of convenience to me. The first reason is its high speed. In cities where congestion(拥挤) is an issue, subway travel is much faster than other modes of transportation(交通), because they can avoid any traffic jams(交通堵塞) in rush hours. Secondly, Subway travel is extremely green(及其环保). Not only is it more environmentally friendly (保护环境的)than automobile(汽车) travel, it is also has the advantage(优势) over public bus systems, as subways do not emit(排放) harmful exhaust fumes(废气) into the air.