According to the data of Committee for natural resources, environmental protection and ecological safety of St. Petersburg Administration the main sources of environmental pollution are mobile objects (447.8 thousand tons versus 73.2 thousand tons stationary) in 2008-2015. During the period growth rate of stationary sources' pollution (58.4%) overtakes mobile vehicle emissions (26.9%) in 2 times. The urban environment seems dangerous. Increasing pollutant emissions in the city is comparable with growth of cars quantity. The share of carbon monoxide has risen to 80.5% in the structure of pollutants from mobile objects yet. At the same time, the share of nitrogen oxide is reduced. The share of the hydrocarbons and volatile organic compounds is almost constant. The goal of the paper is to identify the main trends and the negative impact of transport system on the environment of the region. Optimizing of urban traffic flows and reducing emissions of carbon dioxide as the most voluminous harmful substances can be recommended to improve the harmful environmental situation.