In the short term, the best strategy for reducing demand for petroleum may be encouraging the trend toward improved efficiency of conventional vehicles. Much of that improvement has resulted from the Corporate Average Fuel Efficiency (CAFE) standards, initially adopted in 1975 and revised in 2007. The standards have recently been made more stringent, with fuel economy requirements increasing annually between 2012 and 2025. A study of the 2017–2025 CAFE standards found that a mid-size vehicle with advanced conventional gasoline engine technologies is likely to meet the increased standards. Regulations aimed at implementing the first standards for model years 2014 to 2018 medium- and heavy-duty trucks—based on analyses from the Transportation Research Board and the National Research Council—are currently in effect and regulations for beyond 2018 are being proposed.