Trends in Transportation - Hydrogen and Fuel Cells: Advances in Transportation and Power - page 146

of the country. It also helped to reduce the effects of suffering from heart
or respiratory diseases.
The boom in suburban home building also had other effects on
energy resources. As large-scale builders cleared the land of trees, the new
homes were subject to more heat and more cold, increasing the energy that
was required to keep the temperature comfortable inside.
AUTO EFFICIENCY
While smaller cars may use less petroleum, they are not inherently
more efficient. Of the energy released in combustion only 12-15% is finally
applied to move the car. Most of the rest is lost due to the thermodynamic
inefficiency of the engine and escapes as heat. The remainder is drained
off by such factors as aerodynamic drag, rolling resistance of tires,
transmission slippage, internal friction, idling, and air conditioning. Just
to push the air out of its way, a car may use 50% of the available energy at
55 mph and 70% at 70 mph.
Large frontal areas create air turbulence and drag. Bodies derived
from wind tunnel testing can provide a more smooth air flow around the
vehicle. Details such as mirrors, rain gutters, trim, wheel wells and covers
can also be more appropriate for air flow. Radial tires can reduce fuel
consumption as much as 3%. Puncture-proof tires of plastic could save
even more and eliminate the cost and weight of a spare tire and wheel.
Automatic transmissions impose a mileage penalty of about 10%
compared to manual gearboxes. Continuously variable transmissions
can provide better mileage. A stop-start engine that shuts down if a car
is idling or coasting can cut gas consumption by about 15%. A touch on
the accelerator restarts the engine. This is done in many modern hybrids.
Better lubricants and bearings can reduce friction, and microprocessors can
monitor systems and make adjustments to keep operation at peak efficiency
without or despite actions by the driver. Computer engine controls are
used in most modern engines but they are optimized for pollution control
and not mileage. The proper maintenance of roads can improve mileage
by 5% but much maintenance is delayed due to funds and the overuse of
our roads from high traffic. Combustion engines operate best at about 45-
MPH and ideally traffic should be speeded up in cities and slowed down
in the country. This is difficult to achieve although possible, low highway
speeds are unpopular and higher city speeds are impractical for safety