美国正在研制既可在电化线路上用集电弓供电、又可在非电化线路上用柴油机驱动的两用机车(DML),计划到1985年付诸实用。使这种机车具有两种机能的理由是:减少投资、节约维修费用,并且操纵也方便。机车的结构,一半是具有集电弓的电力机车,一半是具有柴油机的内燃机车。在电化区 The United States is developing a dual-purpose locomotive (DML) that can be powered by a pantograph on an electrochemical line and diesel-driven on a non-electrochemical line and is planned to be put into practical use by 1985. The reasons for having such two types of locomotives are: reduce investment, save on maintenance costs, and ease of handling. The structure of the locomotive is half that of an electric locomotive with a pantograph and half of a diesel locomotive. In the electrochemical zone