Development of road traffic emission inventories for urban air quality modeling in Madrid (Spain)

Madrid is one of the many urban agglomerations that are struggling to meet NO2 air quality standards in Europe. According to previous studies, road traffic is responsible for 57% of total NOx emissions in the Madrid metropolitan area and up to 90% of NO2 ambient concentration in the city center. Therefore it is utterly important to compile reliable emission inventories for this sector so specific measures and policies can be designed and assessed. This contribution discusses a field campaign made in Madrid to produce accurate input information as well as the models and methods used to compute emissions in a consistent way. The vehicle fleet characterization study made use of already available resources of the Madrid Municipality (traffic cameras in 55 locations across the city). Information of nearly 5 million plates was captured and crossed with the database of the National Traffic Authority to map vehicles into the 199 categories considered by the COPERT 4 software (EMEP/EEA methodology). Traffic intensities and average speed were provided by the regional traffic-demand model used by the Madrid Municipality. Additional information (traffic signs, detail ed vehicle trajectories, signal lights phases, etc.) was collected to feed a microscale traffic model (VISSIM) needed to generate instantaneous speed and acceleration data for a hot-spot (a heavily-trafficked roundabout). Emissions with resolution of seconds and meters were computed with ENVIVER (emission factors from VERSIT+) for this particular area. The results were aggregated and compared with those from the mesoscale model(COPERT) as a preliminary assessment for this approach.