Over the past 16 years, the federal government has invested billions of dollars to build a fleet of 112,000 alternative-fuel vehicles, intended to serve as a model for a national movement away from fossil fuels.

An analysis by the Washington Post newspaper has determined that the project hasn't achieved its goal in terms of decreased gasoline consumption and emission rates.

Under a mandate from Congress, federal agencies have gradually increased their alternative-fuel fleets, with a majority of them going for flex-fuel vehicles. These are capable of running on either gasoline or ethanol-based E85 fuel.

The most commonly available blended fuel for use in flex-fuel vehicles, E85 is a blend of 85% ethanol and 15% gasoline.

However, many of these vehicles were sent to locations hundreds of miles from any alternative-fueling sites.

Consequently, more than 92% of the fuel used in the government's alternative-fuel fleet continues to be standard gasoline, the analysis found.