Measuring and Modelling Vehicle NOx Emissions Using a Remote Sensing Device

Despite the increasingly stringent type approval limit val- ues for vehicle emissions no quantitative difference has been seen in roadside concentrations of NOX concentra- tions (Carslaw et al., 2011b). This thesis aims to improve the ability of measuring and modelling the NOX emissions of passenger cars in urban environments by taking an in depth look at the emissions of vehicles observed in real driving environments over a number of years in Aberdeen, Cambridge, Leeds and Sheffield using a Remote Sensing Device. The remote sensing device is tested under con- trolled conditions to ascertain it’s measurement accuracy for both pollutants and vehicle specific power. A mathe- matical distribution function for describing the emissions of a fleet is presented and shown to be a good description of over 90% of the vehicles and a superposition of two of these distribution functions was able to describe the distribution of the rest of the fleet’s N O emissions with a high degree of accuracy. The distribution functions derived for one city were used to create a predictive model to determine how the average emission of a passenger car fleet vehicle per- formance would evolve over time showing that by 2025 a ≈ 30% reduction in NOX could be expected if the fleet was allowed to evolve naturally.
In addition to these results a number of real world prob- lems were assessed using the new framework developed in this thesis. The emissions of taxis compared to privately
owned vehicles was assessed with taxis being shown to emit ≈ 50% more NOX than their equivalent vehicles in the fleet. The Volkswagen Group scandal, #dieselgate, is dis- cussed and the data that the remote sensing device has been used to assess the real driving emissions of VWG pas- senger cars fitted with the EA189 engine. The observations show that whilst VWG vehicles are exceeding the limit val- ues in real driving environments, they are observed to have equivalent or lower emissions factors than other marques.