<P> Energy - efficient vehicles may reach twice the fuel efficiency of the average automobile . Cutting - edge designs, such as the diesel Mercedes - Benz Bionic concept vehicle have achieved a fuel efficiency as high as 84 miles per US gallon (2.8 L / 100 km; 101 mpg), four times the current conventional automotive average . </P> <P> The mainstream trend in automotive efficiency is the rise of electric vehicles (all@electric or hybrid electric). Hybrids, like the Toyota Prius, use regenerative braking to recapture energy that would dissipate in normal cars; the effect is especially pronounced in city driving . Plug - in hybrids also have increased battery capacity, which makes it possible to drive for limited distances without burning any gasoline; in this case, energy efficiency is dictated by whatever process (such as coal - burning, hydroelectric, or renewable source) created the power . Plug - ins can typically drive for around 40 miles (64 km) purely on electricity without recharging; if the battery runs low, a gas engine kicks in allowing for extended range . Finally, all - electric cars are also growing in popularity; the Tesla Model S sedan is the only high - performance all - electric car currently on the market . </P> <P> Cities around the globe light up millions of streets with 300 million lights . Some cities are seeking to reduce street light power consumption by dimming lights during off - peak hours or switching to LED lamps . It is not clear whether the high luminous efficiency of LEDs will lead to real reductions in energy, as cities may end up installing extra lamps or lighting areas more brightly than in the past . </P> <P> There are several ways to reduce energy usage in air transportation, from modifications to the planes themselves, to how air traffic is managed . As in cars, turbochargers are an effective way to reduce energy consumption; however, instead of allowing for the use of a smaller - displacement engine, turbochargers in jet turbines operate by compressing the thinner air at higher altitudes . This allows the engine to operate as if it were at sea - level pressures while taking advantage of the reduced drag on the aircraft at higher altitudes . </P>

A measurement of how many tasks a computer can accomplish in a certain amount of time is called a(n)