By using an executive order to state that the US Government will no longer buy automobiles that run on petroleum for the federal fleet, the administration could spur the building of alternative fuel vehicles and the research and development of alternative fuels.
Such an order would create many "green collar" jobs in addition to significantly reducing auto pollution. The cars and fueling infrastructure necessary for such an order will not only be used by the government, it will eventually be adopted by the private sector and used by the general public, in much the same way the internet was.