Korea completed the development of natural gas buses from 1991 to 1997, and after a trial operation of a total of four intra-city buses in Incheon and other areas from July 1998, the absence of exhaust fumes and excellent passenger comfort were welcomed by the public. Natural gas buses were distributed in full scale from 2000 based on the results of the trial operation. By the end of 2013 the government had distributed 34,297 buses and 1,174 cleaning vehicles and installed 479 charging stations throughout urban areas of the country.