中文摘要：

美国东北部城市群多层次轨道交通系统包括城际铁路与区域铁路、市郊铁路和捷运系统以及连接枢纽,各个层次的轨道交通系统服务对象、服务范围明确,线路参数与服务需求相匹配,通过交通枢纽可以便捷换乘。另外,美国也针对各城市群进行整体轨道交通发展规划,进一步完善多层次轨道交通系统。对比我国城市群轨道交通系统发展现状提出建议：亟需确立结构完整和功能明确的系统框架,并以城市群为对象进行统一规划与资源整合。

英文摘要：

The multi-level rail transit system in megalopolises of Northeast United States includes intercity rail, regional rail, subur- ban rail, mass rapid transit and connecting hubs. Each level has a clear service objective and scope： its line parameters can meet the service needs and the transfer is convenient through hubs. In addition, the United States has implemented a development plan to im- prove the rail transit system in megalopolises. After making a comparison between the conditions of rail transit system in megalopolises in China, authors suggest that for China a system with intact structure and explicit functions should be determined, and the planning should be based on the development of the megalopolis as a whole.