Safer Vehicles for People and the Planet Page: 4 of 13
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The cars and trucks plying America's roads and highways generate roughly 20 percent of the
nation's total emissions of carbon dioxide, a pollutant that is, of course, of increasing concern
because of its influence on climate. Motor vehicles also account for most of our country's
dependence on imported petroleum, the price of which has recently skyrocketed to near-record
levels. So policymakers would welcome the many benefits that would accrue from lessening the
amount of fuel consumed in this way. Yet lawmakers have not significantly tightened new
vehicle fuel-economy standards since they were first enacted three decades ago. Since then,
manufacturers have, for the most part, used advances in automotive technology, ones that could
have diminished fuel consumption, to boost performance and increase vehicle weight. In
addition, the growth in popularity of pickups, sport utility vehicles (SUVs) and minivans-and
the large amounts of gas they typically guzzle-has resulted in the average vehicle using the
same amount of fuel per mile as it did 20 years ago.
One of the historical impediments to imposing tougher fuel-economy standards has been the
long-standing worry that reducing the mass of a car or truck to help meet these requirements
would make it more dangerous to its occupants in a crash. People often justify this concern in
terms of "simple physics," noting, for example, that, all else being equal, in a head-on collision,
the lighter vehicle is the more strongly decelerated, an argument that continues to sway
regulators, legislators and many in the general public.
We have spent the past several years examining the research underlying this position-and some
recent work challenging it. We have also conducted our own analyses and come to the
conclusion that the claim that lighter vehicles are inherently dangerous to those riding in them is
flawed. For starters, all else is never equal; other aspects of vehicle design appear to control what
really happens in a crash, as reflected in the safety record of different kinds of vehicles. What's
more, the use of high-strength steel, light-weight metals such as aluminum and magnesium, and
fiber-reinforced plastics now offers automotive engineers the means to fashion vehicles that are
simultaneously safer and less massive than their predecessors, and such designs would, of
course, enjoy the better fuel economy that shedding pounds brings.
Saving Gas, Saving Lives
If a typical car could somehow drop 10 percent of its mass, its fuel economy would increase by
anywhere from 3 percent to 8 percent. (The larger value applies if the size of the engine is also
reduced to keep acceleration performance the same.) Designers are keenly aware of this relation,
and after federal fuel-economy standards were first enacted, automakers virtually eliminated the
heaviest cars (those weighing more than 4,000 pounds) from their new-vehicle fleets. These
behemoths went from 46 percent of sales in 1975 to just 9 percent in 1980, after which only a
dwindling number could be found in showrooms (Figure 1). But in the late 1980s, the sales of
heavier "light trucks," including many of the SUVs used as substitutes for cars, began to
increase. By 2003, the fraction of light trucks weighing more than 4,000 pounds reached 32
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Wenzel, Thomas P; Wenzel, Thomas P & Ross, Marc. Safer Vehicles for People and the Planet, article, March 1, 2008; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc894769/m1/4/: accessed April 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.