Policy measures can support increased supply of and demand for alternative fuels in different sectors or for different fuel types. For example, the potential supply of alternative fuels is insufficient to replace all current fossil fuel use across hard-to-decarbonize sectors. These policy measures will not by definition result in emissions reductions or optimal allocation of fuels across sectors: They must be targeted to facilitate the use of alternative fuels where they would be most effective at reducing greenhouse gas emissions from fossil fuels.