Transportation systems, usually publicly but sometimes privately owned and operated, designed to move large numbers of people in various types of vehicles in cities, suburbs, and large metropolitan areas.
Modern mass transit is an outgrowth of industrialization and urbanization. In the 1830s early mass transit in New York City included horse-drawn buses, which were soon replaced by fixed-rail horse-drawn trolleys. By 1900 motorized bus es had appeared in Europe and America. With the advent of electricity, streetcar s and subway s were introduced in many large cities. In the 20th century the automobile 's increasing popularity undermined mass transit development; fixed-rail streetcar systems were widely removed to provide space for cars. Concern over air pollution has revived interest in light-rail transit and has led to regional mass transit systems.