## 5 Critical Analysis of Results and the Sustainability Approach  
As mentioned previously, the decarbonisation of transport is a major economic, societal and political challenge for the EU. The underlying cause of the constant increase in diesel consumption is the nature of the fuel market and the fuel taxation system in the EU. As we have seen, gasoline consumption decreased in all member states (expect one) and diesel emissions increased. High duty on gasoline and lower duty on diesel has contributed to a market-based shift in favour of diesel road transport vehicles. Customers choose diesel vehicles as they are considered better value for money in the long term. This belief in the economy of diesel has led to an increase in diesel emissions. The EU's fuel duty policy is influenced by the long-term goal of obtaining more mileage from diesel fuel and thereby maximising the purchasers' advantage in the oil import market. The fuel excise policy is skewed even though diesel has a higher CO\({}_{2}\) emissions factor than gasoline: 74,100 KgCO\({}_{2}\)/T) for diesel and 69,300 KgCO\({}_{2}\)/T) for gasoline. The carbon content of diesel is also higher than that of gasoline, while the net calorific values of diesel and gasoline are similar. The EU does not gain any substantial advantage by consuming more diesel nor does it have any particular incentive to do so. The results do not take into account the number of diesel and gasoline cars in each EU member state, the number of miles travelled by the cars and the specific economic drivers that lead to the emission of GHGs. The methodology estimates the total amount of energy and emissions to measure GHG emissions. To overcome the climate change challenge, the EU must avoid these emissions, and the prevailing sustainability policy falls short when addressing the climate sustainability challenge. According to the Global Carbon Budget [27], a reduction of 1-2 GtCO\({}_{2}\) is needed to achieve the goals of the Paris Agreement. At present, there is a real risk that road transport GHG emissions will consume the majority of the EU's carbon budget [8]. One study calculated the EU's carbon budget for 2010 to 2100 as being 83 Gt and 116 Gt for the 1.5 \({}^{\circ}\)C and 2 \({}^{\circ}\)C scenarios, respectively [28]. Another study calculated the EU's carbon transport budget as being between 10.2 and 12.1 GtCO\({}_{2}\)e, which included aviation, rail and navigation emissions [29]. The results in Table 1 and the Appendix A show that the total carbon emissions for road transport in the EU in 2000 and 2018 were 0.23 GtCO\({}_{2}\)e and 0.24 GtCO\({}_{2}\)e, respectively. These totals do not include aviation, shipping and navigation emissions. This indicates that BAU annual road transport emissions in the EU are in the range of 0.23-0.24 GtCO\({}_{2}\)e. It should be noted that these emissions will decrease as the United Kingdom is no longer an EU member state. The BAU trajectory of road transport carbon emissions in the EU is outlined in Table 2. There are limitations to the BAU scenario, however, as it assumes that long-term carbon emissions will remain at 0.23 or 0.24 GtCO\({}_{2}\)e per year. In addition, the results shown in Tables 1 and 2 may vary as default emission factors were used to calculate the CH\({}_{4}\) and N\({}_{2}\)O emissions. If the rate of carbon emissions does not decrease, the EU will have used up its allocated carbon transport budget by the early 2060s. Road transport emissions will consume a significant part of EU's total carbon budget.