A Rail includes "heavy" and "light" transit Rail. Heavy transit Rail is characterized by exclusive rights-of-way, multi-car trains, high speed rapid acceleration, sophisticated signaling, and high platform loading. Also known as subway, elevated Railway, or metropolitan Railway (metro). Light transit Rail may be on exclusive or shared rights of way, high or low platform, multi-car trains or single cars, automated or manually operated. In generic usage, light Rail includes streetcars, trolley cars, and tramways.

In the environmental context, "rail" typically refers to the transportation of goods and people by trains. Rail transportation can have both positive and negative environmental impacts. Some examples of the environmental impacts of rail transportation include:

1. Lower greenhouse gas emissions: Trains generally produce fewer greenhouse gas emissions per unit of cargo or passenger than other modes of transportation, such as cars or airplanes.

2. Reduced air pollution: Trains produce less air pollution than other modes of transportation, especially when compared to diesel-powered trucks.

3. Noise pollution: Train noise can be a significant source of noise pollution, especially in urban areas where rail lines are close to residential areas.

4. Habitat fragmentation: Rail lines can fragment habitats, disrupt wildlife movement and contribute to the loss of natural habitats.

5. Land use and energy consumption: Rail infrastructure can require large amounts of land and energy, especially for electrified railways.

Similar concepts in the environmental context include:

1. Sustainable transportation: This involves using modes of transportation that have minimal negative environmental impacts, such as trains, bicycles, and electric vehicles.

2. Smart growth: This is an approach to urban planning that aims to create walkable, bikeable communities that reduce the need for cars and promote more sustainable modes of transportation.

3. Transit-oriented development: This involves developing land uses around transit stations and corridors to encourage more people to use public transportation.

4. Infrastructure planning: This involves designing and developing transportation infrastructure, such as rail lines and highways, to minimize negative environmental impacts and promote sustainability.