Portugal is one of the few OECD countries in which electricity intensity (electricity consumption per unit of GDP) increased between 2000 and 2007. From the point of view of energy efficiency, a higher share of diesel vehicles in the fleet means less energy is consumed for the same transport activity (expressed in passenger-kilometres or tonne-kilometres). From the point of view of pollutant emissions, there are strong indications that a larger number of diesel vehicles could result in increased emissions of nitrogen oxides and particulate matter.