Assessment of comprehensive energy systems for achieving carbon neutrality in road transport

•Energy systems focusing on road transport for carbon neutrality are analyzed.•Cost-effective measures for automobiles including offsets by CDR are considered.•Several carbon–neutral pathways exist, even with HEV and PHEV.•Restricting new car sales to BEV only would increase costs considerably. The world is seeking to achieve carbon neutrality by 2050. In general, electrification is a key measure in all sectors. Meanwhile, there are several emissions reduction options also in the road transport sector to achieve carbon neutrality when considering the energy system as a whole. Hydrogen, hydrogen-based synthetic fuels, and bioenergy can serve as alternative energy sources, and carbon dioxide removal (CDR) technologies, including direct air capture, can offset CO2 emissions from petroleum fuels. Comprehensive analyses that consider outlooks for both automobiles and energy supply with spatiotemporal variation are thus needed to explore possible strategies for the rational achievement of carbon neutrality. Our analyses, based on the integrated assessment model DNE21+, show that, although battery electric vehicles (BEV) are important, hybrid and plug-in hybrid vehicles, accompanied by the introduction of CDR and synthetic fuels, can play important roles. Globally uniform regulations for introducing only BEV could hinder cost-effective emissions reduction.