The U.S. government manages a huge fleet vehicles, mostly through the General Service Administration (GSA) which oversee 210,000 vehicles directly. This is a huge opportunity for the government to lead by example and to use its purchasing power to support promising technologies. Back in the spring of 2011, in an effort to bring down costs and reduce the federal fleet's environmental footprint, president Obama ordered federal agencies to give up full sized SUVs and sedans unless "absolutely necessary". The federal government has now announced that it wants federal agencies to increase the number of hybrids in their fleets by about 10,000. That would mean doubling the current 10,672 hybrids that they already have, though hopefully more of the new ones will be much more fuel-efficient plug-in hybrids.
"Providing a hybrid federal fleet is an essential part of the GSA's commitment to making government agencies as efficient and effective as possible," said GSA acting Administrator Dan Tangherlini. "At a time when government needs to make every tax dollar count, GSA is committed to creating more energy efficiency and cost-saving opportunities like the fleet consolidation program that make government smarter and reduce our environmental footprint." (source)
These kinds of measures should be combined with other incentives to shrink the size of the fleet and encourage more walking, biking, public transit, and telecommuting when possible (FBI agents on the hunt for suspects absolutely need vehicles, but I'm sure some federal employees who get a fleet car could easily do without...).