This study evaluates how air pollution in Istanbul for the years 2015 and 2030 will be impacted upon by decreasing automobile usage through the Marmaray Project, which is a new transport system to pass through Europe to the Asian continent. To investigate the effect of the project, the existing transportation situation in Istanbul was determined, and then an emission calculation was performed for the city regarding the cases of "with" and "without" the.. Marmaray Project for 2015 and 2030. The emission factors and calculations were performed for three types of pollutants, criteria pollutants (CO, VOC, VOC-evaporated, NOX, SOX, PM), toxic pollutants (1,3-butadiene, acetaldehyde, formaldehyde, NH(3), benzene) and greenhouse gases (CO(2), CH(4), N(2)O), by applying the International Vehicle Emission modeling technique. The obtained results were evaluated according to pollutant types, road type and driving modes. According to the modeling results, the rate of decrease in emissions will be 12.4% in 2015 and 11.6% in 2030, for all types of pollutants. Because of the increasing usage of gasoline engines, criteria pollutants will be higher, especially in the start mode. The most important factor for toxic pollutants was fuel type, and the decreasing emissions of toxic pollutants will be created by decreasing automobile usage. The development of vehicle technology will cause a decrease in the emissions of greenhouse gases. When the existing situation was compared with 2015 and 2030, it was clearly seen that the emission rate of the "without the Marmaray Project" situation had a much faster increase than that of "with the Marmaray Project".