Indianapolis’s entire vehicle fleet may soon run on alternative fuels.

City mayor Greg Ballard is pushing the conversion, something that has not been done yet in a major American city, and he wants it done by 2025. Other cities all have green fleet programs, but none encompass every single vehicle in the fleet.

The plan works like this, says Governing magazine: “The first step is moving about 500 city-owned sedans to plug-in or hybrid vehicles. A newly signed executive order requires the city to make that switch as older vehicles are phased out. Next, the city will move heavy fleet vehicles — like fire engines and garbage trucks — to compressed natural gas. And the final step — and possibly the trickiest one — is the conversion of its police vehicles.”