Hohhot, capital of North China's Inner Mongolia Autonomous Region, will start building its first subway lines next year, the city government said on Thursday.The proposal includes two lines stretching about 60 kilometers in the city of 3 million, according to the government.Hohhot's economy has soared in the last decade as the resource-rich region boomed during China's construction and investment binge. The city now has more than 900,000 cars and faces frequent traffic jams downtown.Hohhot Mayor Qin Yi said the metro project has met the review and approval requirements for the National Development and Reform Commission Qin added that the metro project has passed evaluations by the Ministry of Housing and Urban-rural Development as well as assessments by environment watchdogs.