The two locomotives are now zooming along a 62-mile stretch of track in Germany.
All aboard: Created by French company Alstom, the two trains will be running on a stretch of track previously used by diesel powered vehicles. The hydrogen engines can hit a top speed of 140 kilometers per hour (87 miles per hour) and the trains have a range of about 600 miles, which means they can make about nine trips on a single tank.
How it works: The vehicles are powered by fuel cells that combine hydrogen and oxygen to produce electricity. Extra energy is stored on board in batteries for later use.
Why it matters: While the trains are more expensive, they are cheaper to run and could help minimize harmful emissions: they only pump out steam and water. Alstom plans to provide Germany with another 14 hydrogen trains by 2021, and France plans to debut its first by 2022.
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