Introducing autonomous buses and taxis: Quantifying the potential benefits in Japanese transportation systems

The introduction of autonomous buses and taxis is expected to generate such benefits as cost reductions—and particularly for regional bus operations with a substantial deficit—as well as enhancing public transit accessibility through decreased trip costs. The purpose of this paper is to provide an overview of the impacts of introducing autonomous buses and taxis on metropolitan transportation systems by quantifying the costs of travel in Japan, and to discuss the potential benefits. First, this study sets the assumptions on autonomous driving technology, including its impacts on vehicle costs, the decreased labor costs for driving and safety monitoring in buses and taxis, and decreased driving stress for private car users. Next, operating costs are computed for autonomous buses and taxis in Japanese metropolitan areas. The costs of travel, or the sum of monetary and time costs, are then computed with and without vehicle automation for different trip types in high- and low-density metropolitan areas. The results highlight that the costs of public transit trips that currently have a smaller share of time costs in overall trip costs could decrease considerably due to vehicle automation. For instance, costs for 10–20-km trip lengths could decrease by 44–61% for taxi trips and 13–37% for rail/bus trips with taxi access, followed by a decrease of 6–11% for bus trips and 1–11% for rail trips with bus access. Further, private car trip costs could decrease by 11–16%. More substantial cost reductions in rail/bus trips with taxi access could occur in the case of smaller trip distances and/or in residential areas far from stations; larger reductions in rail trips with bus access could occur in low-density metropolitan areas. Finally, it is expected that vehicle automation in more fixed modes of public road transit could primarily benefit the transit industry and government, with such effects as improved labor productivity and reduced subsidies, while vehicle automation in more flexible modes could benefit metropolitan residents as well as the transit industry. This further suggests that a deficit of regional bus operations could be recovered during the transition to the full performance of autonomous buses.