Resumen
Transport is one of the main sectors of the economy, which has a significant impact on the economic development of the country. The increase in the development of transport and transport infrastructure itself definitely develops the economic potential of the country, strengthens its economic, social cohesion and economic competitiveness. Depending on the type of emitted substances, transport pollution is of local or global nature. Considering the emission of pollutants in urban agglomeration, emitted toxic compounds mainly impact the local pollution of the environment. The primary toxic pollutants emitted into the environment from combustion of fuels include mainly: carbon monoxide CO, aliphatic and aromatic hydrocarbons (including benzo(a)pyrene), sulphur dioxide SO2, nitric oxide NOx and particulate matter PM (soot, tar) and heavy metals. The paper is focused on model of urban freight transport influences on city environment. The road, as a line source of pollution, is included in the model with a set of emitters and concerns finite straight line with a constant source of emissions per unit length and a constant effective source height. In order to perform modelling it is necessary to divide vehicles into categories, which forms the basis for determining the characteristics of the emission. The model will cover simulation of the distribution of pollutants for vehicle traffic stream in a communication network of the city. In the first case, study will be conducted for the straight sections of road, and then combined into a junction, which will allow for identification of the impact of traffic on air quality in different parts of the urban area. The example area of analysis includes chosen streets in Szczecin city centre. The basis of the analysis are the data collected during the survey and using traffic detectors.