The external costs of car and air travel - implications of legal compliance, energy mixes and travel patterns

Baumgärtner, Frank Andreas; Letmathe, Peter (Thesis advisor); Walther, Grit (Thesis advisor)

Aachen : RWTH Aachen University (2023)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2023


The mobility sector is facing enormous challenges. The aim is to significantly reduce emissions of greenhouse gases and air pollutants in order to make mobility more environmentally sustainable. Due to the increasing mobility needs of individuals, however, emissions in the mobility sector continue to rise. Nevertheless, there are technological innovations that could counteract this trend. The question is: What potential do these innovations have for reducing the externalities of the mobility sector? In this dissertation, the externalities of mobility technologies are analyzed. The focus is on externalities from the use phase of passenger cars and passenger aircraft within Europe. The externalities are assessed by means of external cost rates. This not only allows the results to be aggregated in a comprehensible way but also makes it simple to derive recommendations for action for various stakeholders. A research model is successively built up over a total of four research papers. There are emissions limits for conventional vehicles with diesel or gasoline engines that must be fulfilled for registration in the European Union. In the case of diesel vehicles in particular, there has been systematic manipulation in the past. Research Paper 1 analyzes the external costs of vehicle use for 49 real vehicles in Germany. The focus is especially on diesel vehicles. The research paper examines to what extent the external costs of these vehicles differ regarding relevant test bench emissions for the registration and assumed real driving emissions. Furthermore, the external costs of diesel vehicles are compared with those of gasoline and battery electric vehicles. It can be observed that diesel vehicles with assumed test bench emissions cause relatively similar external costs as those of battery electric vehicles. The external costs of gasoline-powered vehicles are higher in comparison. However, these results change significantly when real driving emissions of diesel vehicles are assumed. In this case, diesel is the powertrain with the highest external costs in all vehicle classes. The additional costs caused by increased NOX emissions amount to approximately 1 cent per km. Overall, this results in additional external costs for Germany of around €2.5 billion per year due to the so-called Dieselgate. The electricity sector is the largest emitter of climate gases and air pollutants. Among the individual European countries, there are large differences in the generation of electricity and the associated emissions. Furthermore, there are significant transformation processes in electricity production within these countries. Research Paper 2 calculates the external costs of electricity in 27 European countries from 2010 to 2030, combining country-specific power plant technology data, country-specific energy mixes and country-specific external cost rates in the model. On average, external costs amount to about 8 cents per kWh. However, it can be seen that there are significant discrepancies between the external costs in the individual countries and the way they develop. Overall, only a small number of countries have succeeded and will succeed in significantly reducing their external costs, as this requires ambitious transformations. Deeper insights can be gained by grouping the energy generation technologies into five basic technologies and dividing the external costs into climate-impacting global and local external costs. For reducing emissions from the mobility sector, electrification is a crucial factor. Research paper 3 combines the research approaches from research papers 1 and 2 with further data to estimate the environmental potential of battery electric vehicles. For this purpose, the external costs of vehicle use in 27 European countries between 2010 and 2030 are determined. In particular, 31 real-world vehicles with different powertrains are compared. In most countries, battery electric vehicles improve during the period compared to their conventional counterparts. This can be attributed to the fact that the external costs of electrified vehicles are essentially determined by those of electricity production. Improvements in electricity thus affect the operation of battery electric vehicles. For conventional vehicles, this would require special synthetic fuels. It can be seen that in countries with a high share of renewable or nuclear energy, the use of battery electric vehicles is beneficial during the entire study period. In other countries, the use of battery electric vehicles is not yet environmentally beneficial at the beginning of the period, but the relative improvement compared to conventional vehicles changes this within the study period. Even in 2030, the use of battery electric vehicles is not yet beneficial in all countries; countries that obtain a high share of their electricity from coal-fired power generation are the exception. Many long-distance journeys within Europe are also traveled by commercial aircraft. Aircraft are subject to particular controversy in current environmental policy discussions. Research paper 4 analyzes the external costs of selected exemplary air routes within Europe and compares them with those of conventional vehicle travel. For this purpose, the previous findings of research papers 1 and 3 are incorporated into the model. In addition, the previous assumption that a vehicle is only used in one country is relaxed. For the passenger aircraft, we use extensive external data sources to model a three-dimensional flight path and the resulting emissions. The results show that even when a vehicle is occupied by only one person, it has advantages over an airplane for short distances, but this trend reverses for longer distances. The energy-intensive landing and take-off cycle, which occurs for all air routes regardless of distance, explains this trend. Furthermore, the internalization of external costs of air travel within Europe through taxes and charges is analyzed. The analysis shows that existing measures are only suitable to a limited extent for effectively internalizing external costs. In summary, this dissertation enhances the existing research on the external costs of mobility. For this purpose, a comprehensive model is established by four research papers, which can be further extended in the future. The dissertation provides valuable insights for research and practice.


  • Chair of Management Accounting [812110]