Indianapolis is the first city in the US to mandate the conversion of its fleet to clean vehicles.
Mayor Greg Ballard issued an executive order that says any new vehicles purchased for its municipal fleet must electric or plug-in hybrids.
Although the mandate exempts buses and police cars, the city is looking for an industry partner to develop solutions for these applications too. Police cars currently average just 10 miles per gallon (mpg) - reaching 40 mpg would save $10 million in fuel costs.
Heavy vehicles such as snow plows, garbage trucks and fire engines are being converted to run on compressed natural gas.
Ballard's goal is for the 500-vehicle fleet to be modernized by 2025, estimating savings of $12,000 per vehicle over that time.
These vehicles have multiple benefits of reducing the need for foreign oil, lessening the city's environmental impact and cost-savings over the life of the vehicle, says the Executive Order. It is a model that other cities will hopefully duplicate, it says.
Indianapolis is also one of the top communities for electric vehicle infrastructure, with more than 200 EV charging stations.
Houston, Chicago and Los Angeles are also greening their fleets, but New York, which was a leader in this area, has taken a step backward by phasing out its hybrid taxi fleet.