facturers and their suppliers must have been able to make adequate capital investments for bringing new production capacity on line. Typical product-development times for individual automotive products are 3–5 years, but to deploy a new-vehicle technology across all product platforms and vehicle classes usually takes more than a decade, unless mandated by law.
Even when new or improved vehicle technologies are available on the market, barriers to purchasing them include high initial cost, safety concerns, reliability and durability issues, and lack of awareness. Reaching a substantial fraction of vehicle sales usually takes more than a decade unless mandated by law or made possible by clear consumer demand for the new or improved technology.
In the transportation sector, the potential for reducing fuel consumption resides both in increasing the efficiency with which liquid fuels (especially petroleum) are used and in shifting some of the vehicle fleet’s energy demand to electricity. The greenhouse gas emissions and other environmental effects of such a shift depend on how the electricity (or hydrogen, if fuel-cell vehicles are used) is generated.
An extensive menu of technologies exists today for increasing energy efficiency in transportation. Even so, improving new-vehicle fuel economy substantially is a challenging task. A continued decrease in fuel consumption (and associated greenhouse gas emissions) beyond 2020, when the EISA standards must be met, will require that the historic emphasis on ever-increasing vehicle power and size virtually be abandoned.
In the near term, reductions in fuel consumption will come predominantly from improved gasoline and diesel engines, superior transmissions, and reduced vehicle weight and drag. Evolutionary improvements in gasoline internal-combustion engine vehicles are likely to prove the most cost-effective choice for reducing petroleum consumption in the 2009–2020 timeframe. Gasoline-electric hybrids will play an increasingly important role as their production volumes increase and their cost, relative to conventional vehicles, decreases. Meeting the EISA standards is likely to require that, over the next decade or two, an ever-larger fraction of the new-vehicle fleet be hybrids or plug-in hybrids.