Shenzhen, a megacity of China, has already made great efforts to promote the green transport transition, including via the LNG heavy duty trucks (HDTs) program, which may be the largest alternative fuel vehicle promotion program in the world. The economic and environmental impacts of LNG HDTs were analyzed in this study. The results revealed that, while the capital cost of LNG HDTs is higher than that of diesel HDTs, the aggregated cost during the entire operation period of LNG HDTs is 10% to 17% lower than that of diesel HDTs.