EVOLUTION OF TRAFFIC FLOWS AND TRAFFIC-INDUCED AIR POLLUTION DUE TO STRUCTURAL CHANGES AND DEVELOPMENT DURING 1993-2006 IN TARTU (ESTONIA)

Traffic is the main factor affecting air quality in most cities. After the Estonian re-independence in 1991, the increase of motorization has been fast and car usage has intensified. During the same period, the average age of cars has decreased and thanks to improvements in engine technology, the emissions per km have been reduced. The objective was to see how these factors have reflected in air quality. This paper also aim to present an analytical approach to estimate the air pollution levels in recent years, when air quality monitoring has not been conducted, and available traffic data are limited. Based on traffic counts in 25 points across the city the amounts of traffic were modelled for 680 street segments with CUBE software. As air quality is monitored it-regularly in Tartu, dispersion modelling was used to estimate pollution levels. Annual concentrations of exhaust particles (PMexhaust), particulate matter (PM10) and nitrogen oxides (NOx) in 1993, 2000 and 2006 were calculated with AEROPOL software. The traffic increase in the city centre of Tartu was especially rapid in the 1990s. In recent years, it has slowed due to congestion. Overall, traffic levels have increased more than 3 times since 1993. In residential areas, the increase is still rapid - up to 6 times from 1993 to 2006. However, the changes in air quality are less dramatic. Increases from 1993 to 2000 were followed by stable or slightly increasing pollution levels in recent years, especially in case of PMexhaust. The study showed that 2 factors, namely, increase of traffic and improvement of vehicles, have been compensating each other in the dynamics of air pollution.