Greenhouse gas emissions from Spanish motorway transport: Key aspects and mitigation solutions

The current increasing importance of road transport in the overall greenhouse gas (GHG) emissions has led to the adoption of diverse policies for the mitigation of global warming. These policies focus in two directions, depending on whether they involve the reduction of emissions or the mitigation through carbon dioxide (CO2) sequestration. In this paper, the Tier 3 methodology from the European Monitoring and Evaluation Programme and the Environment Agency (EMEP/EEA) was applied to determine the evolution of Spanish motorway GHG emissions in the period 2005-2010. According to the results, though the average daily traffic (ADT) is the major parameter, the average fleet age and vehicle size also affect the level of emissions. Data analysis also revealed a clear connection between the decrease in European trade volume during the financial crisis and the GHG release, despite its temporary character. Among the three improvement scenarios evaluated, reduced speed limit seems the most direct measure while the consequences of afforestation strongly depend on the traffic density of the stretch of the motorway considered. Finally, technological improvement requires a drastic change in the fleet to obtain substantial decrease. The combination of different policies would allow a more robust strategy with lower GHG emissions.