interview > greene > greene 4
Greene 4 (2:15)
Topic(s): Future Transport / Government
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I think there's still an enormous potential for
improving energy efficiency in transportation. Professor John Heywood at MIT
points out that only about 16% of the energy in gasoline gets converted into
useful work at the wheels of a vehicle. And when you consider that the payload
of a passenger vehicle, the one passenger or so—1.2, I think, in the
United States is the average occupancy of a vehicle. So this payload weighs
about one-sixteenth of the weight of the vehicle. So the overall energy efficiency
of our light duty vehicles (cars and light trucks) is about 1%. And we ought to
be able to improve on that a lot. And we can.
Most likely, we would want to focus first, and we have in
the past focused first, on the fuel economy of the vehicle itself. And there we
made, after the first oil crisis in 1973-74, we made enormous progress in
improving the efficiency of vehicles, almost doubling the fuel economy in miles
per gallon of passenger cars, and 60-70% improvement in light trucks. We can
do, in the next 10 or 12 years, we can do another 50% increase without having
to make smaller or lighter vehicles, just by more efficient engines, more
efficient transmissions, slipperier shapes, reduced rolling resistance, and
taking some weight out of cars with material substitution. We can over that
period, maybe by 2017-2018, increase new vehicle efficiency by 50% or so.
And then I think we have to keep going beyond that and
shoot for a goal of perhaps 100% improvement in efficiency by 2025 or 2030.
Because these problems—because of the growth of transportation
continues to grow all the time, we can't just make a certain efficiency
improvement and then rest on our laurels and say, "Okay, we're
done. We don't have to do any more." We have to keep going. But
there's a lot that can be done.