MARICOPA, AZ - Maricopa County will replace its fleet of vehicles with hybrids and other fuel-efficient vehicles, the Board of Supervisors recently decided, according to The Arizona Republic.

Over time, the county's 2,000 cars, sport utility vehicles and trucks will be swapped for less-polluting vehicles rated by the Environmental Protection Agency's Green Vehicle Guide.

Instead of making purchasing decisions based mostly on cost, supervisors will weigh environmental costs before they OK funding for new vehicles.

The county's fleet travels 25 million miles a year and puts out more than 30 million pounds of emissions, both pollutants and greenhouse gases.

County officials estimate they could cut that down by between 3 million and 15 million pounds a year, depending on how much they can afford spending on the more-efficient cars, which tend to cost more.

"We're just owning up to our fraction of the total amount of emissions," said Daren Frank, administrative director for the county's Regional Development Services Agency.

"These pollutants, when they combine with each other and other elements in the air, create haze and greenhouse gases. It gets worse as we end up having to service things farther and farther away as development occurs."

Local governments across the country are responding with policies to combat global warming and lower pollution as public awareness has increased, and going green has become more fashionable, national experts said.

Counties from Washington to Virginia have put in place a wide range of plans that include everything from alternative-fuel vehicles to "green purchasing policies" that require energy-efficient light bulbs, recycled paper and pens made out of recycled plastic.

"They're more aware and trying to do more about it, and they're taking action, not just talking about it," said Abby Friedman, program director of the National Association of Counties in Washington, D.C.

Maricopa County's new policy allows officials to buy a range of cleaner vehicles, from the most fuel-efficient unleaded vehicles to biomass-fueled vehicles to hybrids.

It's too early to tell how much money the county will spend on the effort, officials said.

One scenario puts the cost estimate of replacing all 312 of the county's small and midsize cars with the most-efficient vehicles at $7 million over a decade. Under that scenario the county would save about $1.1 million in fuel costs and 1.3 million pounds of emissions.

The county's fleet includes 32 classes of vehicles, ranging from small compact cars such as Ford Focuses, to large SUV Suburbans to heavy duty semitractor-trailers.

Vehicles are replaced when they reach 10 years, or 100,000 miles. Replacements likely will begin within six months.