The impact of urban transportation on air pollution and the role of subway inits control (Tehran, Beijing, Barcelona)
Many scholars believe that air pollution can be defined when it is mixed with technical indicators. Therefore,in his legal dictionary, Garner has defined air pollution as any material and harmful energy that directly or indirectly emit in the air in such as a way that harm the environment, welfare, or public health. Air pollution has both natural and synthetic origin. In the meantime, transport is one of the causes of pollution that is in artificial emissions group and has a major contribution to air pollution.Urban rail transportation is considered as an efficient factor in reducing transport-related pollution, and thusin addition to its ability in rapid and massive transportation, subway can play an important role in sustainable urban development. In this article, we have tried to examine the role of transportation in urban air pollution as well as the subway role in reducing these emissions, and subways in Tehran, Beijing, and Barcelona have
been investigated and the outstanding role of subway is identified because of the high volume of human transportation and reducing traffic in the city.
Key words: transportation, air pollution, subways, traffic