Towards a GHG-neutral German transport sector: Modelling possible pathways and scenarios

Kurzfassung

In line with its commitment to global climate action and the Paris Agreement, the European Union aims to become climate-neutral by 2050. Various member states have committed to even more ambitious plans in this sense, with the German Climate Change Act in 2021 setting the goal of already achieving greenhouse gas (GHG) neutrality by 2045 and by 2030 reducing emissions by 65 percent compared to 1990 levels. Emissions savings in the transport sector will pose a significant challenge, since in this sector there have been no noteworthy reductions in the past decades, with improvements in vehicle efficiency having been offset by an increase in (road) transport demand. This paper presents findings from a comprehensive study on possible pathways towards GHG neutrality in Germany with a specific focus on the passenger transport sector. Using a bottom-up modelling approach we investigate the potential of various technological pathways and policy options to contribute to the required reduction of emissions. The technological pathways mainly address the topic of vehicle drivetrains (vehicle fleet electrification and usage of alternative fuels) while the policy options also include measures towards a modal shift and traffic avoidance. We develop scenarios that achieve GHG neutrality by 2045 and compare the contribution of the various policy instruments towards this goal. To investigate the impact of the technological pathways and policy options on GHG emissions we employ an integrated model environment consisting of a vehicle stock, a travel demand and an energy consumption and emissions model. The vehicle stock and travel demand models consider user preferences on one side and the supply characteristics (e.g. technology costs, pricing schemes, travel times etc.) on the other side and thus realistically depict the impact of changes in a wide range of parameters. The models provide results in terms of new vehicle registrations and stock by drivetrain, passenger kilometers travelled by mode, energy consumption by fuel type and GHG emissions as yearly values aggregated at national level for Germany in 5-year time steps up to the year 2045. In a middle-of-the-road and (relatively) conservative "Technology Mix" scenario, GHG neutrality is achieved mainly by vehicle fleet electrification, which in turn occurs primarily due to fiscal regulations (e.g. carbon tax, subsidies for vehicle purchases) but without any explicit focus on a specific drivetrain technology. However, as in this scenario there is still a sizeable share of ICE vehicles in the fleet by 2045 (ca. 15 percent of private cars), GHG neutrality can only be achieved by powering these with synthetic fuels, which in turn increases the burden on the energy sector, energy demand and thus also the energy prices. In addition to the "Technology Mix" scenario we present various policy options to achieve either a reduction in road/car travel demand or an even faster diffusion of electric vehicles and alternative fuels. The model results indicate that the former could be achieved for example by improving local public transport services and offering them free of charge or by imposing a road toll on all roads. The latter could be attained by a more aggressive roll-out of charging infrastructure, tighter emission performance standards and increased subsidies. We estimate emission reductions for several policy options including congestion taxes in cities, improving rail and cycling infrastructure, work from home regulations etc. and for selected combinations of policies. Overall, GHG neutrality by 2045 seems achievable even without drastic modal shift and avoidance policies. However, interim emission reduction goals in the short- and mid-term cannot be achieved on this path and will likely also be missed despite all efforts to accelerate the uptake of electric vehicles. Furthermore, the most recent developments on the energy market have increased the importance of energy savings due to the scarcity of resources and increased prices. Against this backdrop, push and pull measures regulating car transport must be carefully considered in order not to overburden transport users. The impact of the policy measures presented in this study could form a valuable input in the upcoming discussions in this regard.