California-based electric busmaker Proterra just scored $55 million through a funding round backed by BMW i Ventures and Al Gore.

Proterra announced yesterday the funding was led by Generation Investment Management LLP, which was joined by BMW i Ventures, the German automaker’s corporate venture capital team.

Former Vice President Gore serves as chairman at Generation Investment Management, a long-term, sustainability focused investment firm.

“More than ever before, cities are looking for sustainable transportation solutions that can reduce pollution efficiently and effectively. Proterra is incredibly well positioned to help accelerate the growth of sustainable cities and continue our transition to a clean energy economy,” Gore said.

The busmaker has been doing well in seeking financial backers. Proterra said that the $55 million Series 6 round has just closed, and that it followed on the heels of an “oversubscribed” $140 million Series 5 in January. That means the Series 5 security was underpriced or in greater demand than had been expected at its launch.

The new funding round will support its east and west coast production facilities and its commitment to creating technology innovation. Those facilities are located in South Carolina and Los Angeles. Tech innovation will be carried out at its headquarters office in Silicon Valley.

Proterra claims to have 60 percent of the market share in North America’s electric transit market; with Chinese manufacturer BYD likely coming in second.

The company reports having sold more than 400 Proterra electric buses across the country including Seattle, Dallas, Nashville, San Jose, Philadelphia, and Reno.

Proterra says it will remain committed to cultivating a talented workforce. That talent has been behind the recent launch of the autonomous bus development project in partnership with the University of Nevada, Reno, Proterra said.

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Generation Growth Equity has been investing in startups for several years through its mission of “embedding sustainability into mainstream capital markets.” Other investments have included electric vehicles, bike sharing, and fleet management technology.

This is BMW i Venture’s first investment in heavy duty EV manufacturing. The company said that it ties into support it wants to show for electric mass transit.

“BMW i Ventures invests in companies that will transform mobility and transportation, and Proterra is pushing the mass transit industry forward with the most innovative heavy-duty electric bus,” said Zach Barasz, partner at BMW i Ventures. “Due to Proterra’s efforts, electric mass transit is overtaking fossil-fuel buses as the new standard.”