SoftBank is doubling down on its self-driving bus project in Japan. SB Drive, an entity created last year to develop autonomous vehicle technology for public transport, just got a cash windfall after Yahoo Japan led a 510 million JPY ($4.6 million) investment.

Yahoo Japan, the Yahoo affiliate which is one of Japan’s most influential tech companies, provided 490 million JPY ($4.4 million) with SoftBank itself ponying up the remaining capital to retain a majority share. Post-investment, SoftBank’s stake in the business stands at 51.1 percent, Yahoo Japan owns a 48.6 percent share, and founding partner Advanced Mobility retains 0.3 percent.

SB Drive is a self-driving project with a focus on making public transportation options, particularly in more rural areas, smarter. The company is aiming to conduct tests on public roads next year with the eventual target of a commercial service by 2020.

Already, it said, it has run “social trials” and testing using fixed-route public buses and freighter trucks that make use of autonomous driving tech. SB Drive has also struck partnerships with four municipalities in Japan.

Beyond adding capital to the business, Yahoo Capital has the potential to be an important strategic partner. Yahoo Japan plans to link SB Drive with its popular Yahoo Maps service, and use related data — such as weather, vehicle congestion, foot traffic, and events — to help with bus planning and deployment.

While there haven’t been major self-driving bus initiatives of this scale in the West, Japan has different social issues to contend with. SB Drive is focused on offering some support in response to Japan’s aging population problem. Today, one-quarter of the country’s population is over 65. That figure, which is higher in some rural regions, is forecast to reach 40 percent nationwide by 2060 meaning that, particularly outside of urban areas, many citizens will require additional help.