Sound Transit announced Tuesday afternoon that starting in 2019, the Link Light Rail trains will run on entirely carbon-neutral energy sources.

The transit agency just signed a 10-year deal with Puget Sound Energy (PSE) to buy wind energy through the Green Direct program.

This is great news for public transit commuters with green living in mind. Even though riding the train is much more environmentally sound than driving in a car alone, there’s still a carbon footprint to many public transportation methods—whether they run on energy or gas.

Sound Transit as a whole already had a pretty small footprint. In 2015 the agency used 84 percent of its energy from carbon-neutral sources, a spokesperson for Sound Transit told Curbed Seattle.

The deal signed today makes the current Link line carbon-neutral. As light rail expands to different areas, we’re told, they’ll work on expanding their agreement with PSE.

Sound Transit’s 2015 sustainability plan, as well as the Sound Transit 3 plan approved by voters in November 2016, puts the agency on the hook for running entirely carbon-neutral by 2030.

The agreement has no capital cost and will actually help stabilize energy costs, said Sound Transit—and may reduce operating costs in the long run.

Other trains powered by wind include the Dutch national railway, which began operating on 100 percent wind energy earlier this year—the first ever to do so. Santiago, Chile’s subway system will get 60 percent of its energy from a combination of wind and solar starting next year.