From Here to Efficiency: Time Lags Between Introduction of New Technology and Achievement of Fuel Savings

The energy savings of new technology offering significant improvements in fuel efficiency are tracked for more than 20 years as vehicles incorporating that technology enter the fleet and replace conventional lightduty vehicles. Two separate analyses are discussed: a life-cycle analysis of aluminum-intensive vehicles and a fuel-cycle analysis of the energy and greenhouse gas emissions of double versus triple fuel-economy vehicles. In both efforts, market-penetration modeling is used to simulate the rate at which new technology enters the new fleet, and stock-adjustment modeling is used to capture the inertia in turnover of new and existing current-technology vehicles. Together, these two effects—slowed market penetration and delayed vehicle replacement—increase the time lag between market introduction and the achievement of substantial energy savings. In both cases, 15 to 20 years elapse before savings approach these levels.