Vehicle fleet characterization study in the city of Madrid and its application as a support tool in urban transport and air quality policy development

Road transport is one of the main sources of atmospheric emissions especially in urban areas where exceedances of NO2 or PM limit values are common. This has evident implications regarding health effects and justifies the need to design and apply effective measures to reduce emissions from mobile sources in urban areas. The methodologies to estimate emissions from road transport require, among other relevant factors, a detailed characterization of the actual fleet composition within the city that vehicle registration databases cannot provide. This contribution presents an experimental campaign to characterise the fleet of vehicles moving in the city of Madrid (Spain). The field campaign made use of different types of already available traffic cameras in the city to record nearly 5 million license plate readings from 1.3 million different vehicles. This information was used to estimate emissions with the COPERT model in the area of study. According to results obtained, passenger cars are responsible for 80.7% of the total mileage made in the city and are also the main contributors in terms of emissions (65%, 73% and 72% of NOx, CO2 and PM2.5, within mobile sources respectively), mainly due to diesel vehicles that represent 68.2% of total passenger cars mileage. The study also provided relevant information on average age and other policy-relevant details such as average emission factors that should be considered to propose effective emission abatement strategies in Madrid City. A comparison with the information obtained from official registration statistics illustrates the need to perform similar studies to gather accurate information of the actual fleet within a city and thus, design sound measures and policies.