Mass transit is a transportation service available to the public for trips generally within metropolitan areas. As with all transportation services, an energy source is a critical input in the production of mass transit trips. Almost all of this energy consumption is derived from burning fossil fuels, a process that emits pollutants affecting human health, visibility, vegetation, and climate change. Transit service is increasingly being scrutinized for its pollutant emissions. Mass transit facilitates travel within densely developed, large urban areas. Because of the existence of mass transit, more intense development within an urban area can occur. Higher-density land use may enable reduced energy consumption when considering the settlement area as a whole.

Forms of Mass Transit

The term "mass transit" generally refers to passenger vehicles that are common carriers in urban areas, as distinct from intercity travel. The terms "public transit" or simply "transit" also are...