Railways have a variety of environmental issues, such as noise, vibration, chemicals, heavy metals, NOx, SOx, CO₂, waste and so on. In order to solve these problems, there are five categories of engineering subjects, namely, analysis of pollutants, assessment of environment, cleanup of pollutants, and preservation, harmonization, and improvement of environment. Several technical themes are also connected with these five subjects, such as life cycle assessment (LCA), recycling, environment conscious materials (ECO-Materials), energy saving, environmental management system, including ISO14001/JIS Q 14001 and so on. This paper discusses not only the engineering and technical aspects but also the economy, culture/tradition, public communications and mission of railways. From these investigations, sound environments can be obtained and finally "Sustainable Development" of our railways is achieved.