H14-238 BOTTOM-UP ROAD TRAFFIC FLOW AND EMISSION CALCULATIONS FOR THE ASSESSMENT OF FUTURE TRAFFIC SCENARIOS AND PUBLIC TRANSPORTATION EXPANSION PLANS IN BUCHAREST

The calculation of road traffic emissions to air has been performed in Romania as part of the national emission inventory and for air pollutant dispersion modeling. The project was focused on the city of Bucharest and includes the major urban roads. Road traffic flows were estimated by means of a traffic assignment model, based on traffic counts carried out at a large number of road sections; the model also estimates the vehicle speeds and the origin/destination (O/D) matrix. The calculated traffic volumes and travelling speeds further feed the atmospheric emissions model, based on COPERT4 methodology. Vehicle exhaust gases are estimated from line sources (corresponding to the main roads of the network) and from area sources (zones of aggregation of O/D nodes giving the contribution of diffuse traffic on the secondary roads). In order to determine the emissions from area sources, the average trip length inside each area was estimated according to the geometrical dimension of the zones (represented by the quarter of the length of the circumference of a circle having the same area) and the extension of the secondary road network (represented by the square root of total length of secondary roads inside the area); this method already showed good results in other national and urban contexts (Doha (Qatar), Kaliningrad (Russia) and Tunisia). The modeling results were compared with real fuel consumption data and the methodology showed good correspondence with Bucharest's figures for year 2006, with an error below 20% of the official fuel consumptions. The small differences could be explained by the portion of local travel not considered by the model, the uncertainties in the distribution of the vehicle fleet as well as on the hypothesis made of the trip lengths. The system was finally used to assess scenarios of future emissions due to the increase in circulating vehicles, which is significantly higher in Romania than in Western Europe, and the impact on traffic flows and emissions related to public transportation expansion policies. As a major result, the system showed that in Bucharest also a moderate expansion of public transportation along the most saturated paths could bring to a considerable decrease of total urban traffic emissions (up to 30% and more).