Urban traffic and air quality evolution under economic recession conditions

This paper deals with the impacts of the current economic crisis on the temporal variation of urban traffic (during 2008-11) and consequently, the impacts on the urban air pollutant levels using as case study the city of Thessaloniki, Greece.

The important temporal variations of the main economic indicators like the annual decreasing trend of the gross domestic product (GDP), the continuous decrease of wages and the labor cost index, the annual increase of unemployment and hence, the decreasing trend of consumption and domestic demand during the current recession period in Greece affect the vehicle traffic.

A considerable decreasing trend of vehicle traffic volume has been observed in all examined intersections of Thessaloniki urban area. The highest temporal decrease of traffic volume is occurred in the morning hours.

The traffic volume decrease determines decisively the concentrations of urban air pollutants and especially, the concentrations of NO₂ (nitrogen dioxide), which has mainly traffic emissions origin and the concentrations of PM10 (suspended particulate matter with aerodynamic diameter less than 10 μm), which has mainly diesel cars emissions origin.

The correlation between traffic and air pollution decreasing trend shows that the air pollutant concentrations decrease is more significant in relation to the traffic decrease due to the fact that, even a small traffic decrease leads to a significant amelioration of the traffic conditions, which lead to significant lower car emissions and therefore, to significant lower pollutant concentrations in the air of the urban area.

The economic crisis did not lead to an increase of the public transport use. It seems that, the traffic decrease of the passenger cars and taxis is due to the trips decrease because of unemployment, the trips decrease connected to lost work positions and the elastic importance trips decrease (shopping, entertainment, etc) during 2008-11.