A low-carbon fuel standard (LCFS) is a rule enacted to reduce carbon intensity in transportation fuels as compared to conventional petroleum fuels, such as gasoline and diesel. The most common low-carbon fuels are alternative fuels and cleaner fossil fuels, such as natural gas (CNG and LPG). The main purpose of a low-carbon fuel standard is to decrease carbon dioxide emissions associated to fuel-powered vehicles considering the entire life cycle ("well to wheels"), in order to reduce the carbon footprint of transportation.