Urban stability in Tehran and public transportation system

In the last years of 20th century, buying automobiles all over the world, in Iran speciallly increases so much. As a result, traffic, pollution, noise, excessive use of dissolvable resources of energy and material, and some others environmental damages introduce, which can be dangerous in the future. In developing countries such as Iran, this is more obvious due to some factors such as weakness in the existing traffic systems, unreasonaable road maintenance, and bad use of vehicles. Introduction of suitable public traffic systems and their use to optimize the existing condittion is one of the ways to improve the condition. With the aim of reducing congestion at city centers, these systems are more effective than any other motor vehicles, according to its energy supply (km/h). Common transportation items at most cities are available which are metro, urban bus, light rail train (LRT). Metros have the ability to transport high volume of passengers inside cities, also they have high speed and regular programs, while they cost so much. Buses are cheaper and more flexible, acceptable volume of passenger transportation, but they seem weaker, LRTs can use in wide range, they are cheaper than metro and seems better than bus and also have more capacity. This study shows that how most of environmmental and pollution problems are related to transportation systems and why optimizing fuel use have not a considerable effect on it alone. Here, it shows that these problems are not related just to the developed and industrial countries, but there are in developing countries as well. And they damage not only their own country, but also the world. We should correct urban substructures in these countries. Finally, we suggest some easy and enforcement policies to optimize public transportation systems at less developed countries (LDCs) such as Iran.