interview > greene > greene 13
Greene 13 (2:57)
Topic(s): Car Culture / Efficiency / Future Transport
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The argument that increasing fuel economy will decrease
highway safety is simply not true. It hasn't been true in the past and
there's no reason for it to be true in the future. Okay? What confuses
people is that it's definitely true that if you run a huge vehicle into a
small vehicle, the occupants of the smaller vehicle are at much greater risk
than the occupants of the large vehicle. However, what I gain by buying a
larger vehicle, heavier vehicle—not a larger vehicle actually.
What I gain by buying a heavier vehicle, in terms of my car colliding with your
car, you lose. So from a societal perspective, okay, this is essentially a
zero-sum game. If I get a heavier car, I'm safer in a collision with you.
You're less safe. Okay. What we know from the history of traffic
fatalities in the US is that the increase in fuel economy we saw on the road
has no correlation with traffic fatalities whatsoever, over the past 50 years.
We have the data now. Early on, there were some
statistical analyses done, but only with the first 4 years of fuel economy
improvements in new cars, not the— not— It takes 15 years
for those fuel economy improvements to come all the way through the fleet. Now
that we have the whole— all of the data, and we can look back to 1960,
and say, you know, "Is there any correlation between fuel economy
improvement and highway traffic fatalities?" Now we know there
And in terms of the safety of individual vehicles and the
role of mass, the weight of the vehicle, and the role of the size of the
vehicle, the best evidence now shows that it would be good to maintain the size
of the vehicles and take a little weight out. Because the, let's say, the
consequences of a crash depend on the ability of the vehicle to slow down the
rate of deceleration of the vehicle, and to slow down especially the rate of
deceleration that the bodies inside experience. So keep them from colliding
with the vehicle itself at a high speed, and slow down the maximum rate of
deceleration in a crash. Having a little space, having some size to the
vehicle, is helpful in that. Having extra mass for a given size is actually
bad, because it means there's more energy that has to be absorbed, so
it's harder for the structure to absorb that energy in a crash. And so what
we understand now is that we would like to keep the size of the vehicles, but
take some mass out. And that's good for fuel economy, to take some mass