In the assumptions regarding the transport, policy both at the level of country and Europe there is the concept of sustainable development of transport. It assumes a balance between social and economic factors and the development of spatial and environmental protection. The transport system, which takes into account the concept of sustainable development, can be called proecological. Warsaw University of Technology in cooperation with Poznan University of Technology performs research work concerning the shaping of environmentally friendly transport system - Project EMITRANSYS. One of its components is to develop a mathematical model taking into account both the minimization of the negative impact of transport on the environment and minimization of the transportation costs. In this model, one of the conditions is to reduce emissions of harmful exhaust gases from transport. The paper identifies the parameters that were used to describe the emission of harmful exhaust compounds by means of transport, in particular by means of road transport. It presents the limits of individual parameters by EURO standard. It also presents the factors affecting the size of the air pollution from transport. In the paper, the areas with excessive concentrations of air pollutants in Poland have been characterized. An analysis of the possible causes of excessive concentrations have been carried out. Areas where traffic should be limited in order to contribute to the reduction of pollution have been identified.