Reductions in CO 2 Emissions from Passenger Cars under Demography and Technology Scenarios in Japan by 2050

Climate policy requires substantial reductions in long-term greenhouse gas (GHG) emissions, including in the transportation sector. As passenger cars are one of the dominant CO 2 emitters in the transport sector, governments and the automobile industry have implemented various countermeasures, including decarbonization of fuels, more energy efficient vehicles, and transport demand management. However, the total impact of these measures in the long term remains unclear. This study aims to clarify the CO 2 emissions reductions from passenger cars by 2050 in 1727 municipalities in Japan under a declining population. To estimate CO 2 emissions, we model travel behavior and traffic situations reflecting the regional conditions of the municipalities, including population density and accessibility to public transport for the base year 2010. Assuming plausible scenarios for future populations and automobile technologies, we estimate CO 2 emissions from passenger cars. We estimate that CO 2 emissions will decline by 64–70% between 2010 and 2050, with automobile technologies playing the largest role. We find that the impact of urban compaction is marginal at the national level but varies by municipality. These results imply that, given regional variations, all countermeasures, including technology and demand management, must be used to achieve the long-term target of CO 2 emissions reductions.