Fuel efficiency standards and the laws of physics

In 1986, the Competitive Enterprise Institute (CEI) waded into the debate over the Corporate Average Fuel Economy (CAFE) standard, which was established in response to the energy crisis of the 1970s. In response to the then-restricted world supply of oil, Congress enacted the Energy Policy and Conservation Act of 1975, which was intended to induce automobile manufacturers to improve the fuel economy of their cars. It set a CAFE standard for passenger cars that increased several times and then leveled off at 27.5 miles per gallon for model years 1985 and beyond.

CEI saw the CAFE standard as an opportunity to make its case that government regulations have unintended harmful consequences and set out to show that fuel efficiency standards were actually killing people. In 1986, CEI filed the first in a series of lawsuits against the National Highway Traffic Safety Administration (NHTSA) aimed at abolishing the CAFE standards. It also persuaded economist Robert W. Crandall to do a study, co-authored with John D. Graham, titled The Effect of Fuel Economy Standards on Automobile Safety, which was published in 1989. The Crandall-Graham study claimed that "CAFE causes 2,000 to 4,000 car occupant deaths each year" because it restricts the production of larger, more crashworthy cars. "We found strong evidence that vehicle weight and safety are correlated," said Crandall. "We found that in the 1989 model year, CAFE reduced the weight of cars by 14%, but that led to a 14% to 20% increase in fatalities in that model year's car."

CEI relies on what it calls "basic physics" to support its claim that heavier cars are safer than lighter cars. "There is no question that if carmakers are forced to build smaller cars in order to meet new, extremely stringent fuel standards that more people will die as a result," said CEI policy analyst Julie DeFalco in a December 1995 news release. "You can't argue with physics -- the bigger the car the safer it is," said institute spokesperson Emily McGee in conjunction with the 1999 release of a CEI study titled ''Deadly Effects of Fuel Economy Standards'.'

CEI's claim is based on Newton's laws of motion, which dictate that when rigid objects of different weights collide, the velocity change of the lighter object will always exceed that of the heavier object, in proportion to their relative weights. If one car is double the weight of the other and they collide at a closing speed of 60 MPH, the heavier car will experience a velocity change of 20 MPH, while the lighter car will experience a velocity change of 40 MPH. Moreover, studies have shown that the risk of death in a collision increases polynomially as a function of velocity change taken to the fourth power. A two-fold increase in velocity, in other words, multiplies the risk of death by 2 to the 4th power, which means that passengers in the lighter vehicle are 16 times as likely to die as passengers in the heavier car.

What this really means, however, is that while heavier vehicles are safer for their occupants, they are actually more dangerous to everyone else--including not just occupants of other cars, but also pedestrians, bicyclists and whatever else they might hit in a single-car collision. Rather than telling us that heavier cars are safer, Newton's laws of motion suggest that optimal safety would be achieved if all cars had approximately the same mass. It is the relative weight of the vehicles rather than their absolute weight that, in theory, leads to the adverse risk consequences for the occupants of the lighter vehicle. This means that if small cars are downweighted and downsized more than light trucks, the increased disparity in weights would increase fatalities. Conversely, however, if trucks are downsized and downweighted more than cars, the greater uniformity would reduce fatalities. There is even some evidence, albeit controversial, that proportionately reducing the mass of all vehicles would have a beneficial safety effect in vehicle collisions.

"There is no fundamental scientific reason why decreasing the mass of all highway vehicles must result in more injuries and fatalities," noted David L. Greene and Maryann Keller, who served on a NRC panel that studied the impact of CAFE standards in July 2001. "In debates about CAFE and safety, it has frequently been claimed that the 'laws of physics' dictate that smaller, lighter vehicles must be less safe. This assertion is quite true from the perspective of a single private individual considering his own best interests and ignoring the interests of others, but it is false from a societal perspective."

When the National Highway Traffic and Safety Administration (NHTSA) reviewed the Crandall and Graham study, it agreed "that all other things being equal, a large car is safer than a small car." The reality, however, is that "all other things" are not equal. In the real world, assessing the impact of weight on auto safety is quite a bit more complicated than a theoretical analysis based on Newtonian physics would suggest. For one thing, the same physical law that makes it harder to change the velocity of heavier cars also makes them harder to brake and maneuver. Added weight adds other risk factors as well. Remember the Ford/Firestone fiasco involving tires that shredded, causing fatal accidents? Those accidents would not have occurred if those same tires were used on smaller, lighter vehicles. In fact, the heaviest passenger vehicles on the market -- SUVs, pickup trucks and vans -- have markedly higher rollover rates than passenger cars because their center of gravity is higher, making them less stable.

"Some maintain that significant increases in fuel economy will require vehicle downweighting which, in turn, will increase injury and death. Others claim that these impacts can be avoided," reported the National Research Council (the most prestigious scientific advisory body in the United States) in a 1992 study titled Automotive Fuel Economy: How Far Should We Go? "The fact that both sides are able to make credible arguments attests to the ambiguity of the evidence available and the complications in attempting to forecast the impacts of future changes in vehicle characteristics," the NRC concluded. "There are no conclusive answers to the question of whether, and to what extent, safety may be compromised by improvements in fuel economy."

There is also good reason to question CEI's underlying claim that fuel efficiency standards force automakers to decrease the weight of their vehicles. Many factors that improve fuel efficiency are independent of weight, and some efficiency factors also carry safety benefits. For example, cars with short acceleration times have high occupant fatality rates, and fuel economy measures that diminish the availability of those cars would probably save lives. "While reducing vehicle weight, all else equal, is clearly one means to increasing fuel economy, so is reducing engine power, all else equal," noted Greene and Keller. In fact, they stated, "The more important technological means to improving fuel economy appear to be neutral or beneficial to safety." Lowering the speed limit on national highways would also improve fuel efficiency and save lives at the same time. The national 55-mph speed limit in effect until 1987 is estimated to have reduced fuel consumption by 1 to 2 percent while simultaneously preventing 2,000 to 4,000 motor vehicle crash deaths annually.

In February 1995, a federal judge ruled against the CEI's attempt to overturn the government's 1990 CAFE standard. "The substance of the CEI's position is intuitively appealing," he stated in his ruling. "We must deal here, however, not with our intuition and not with the petitioners' position in the abstract, but with the concrete record before us. ... That record adequately supports the NHTSA's conclusion that maintaining the 27.5 mpg CAFE standard for MY 1990 would not significantly affect the safety of the motoring public. ... The NHTSA asked the automobile manufacturers to state what specific actions they would take with respect to any model year ... were the agency to lower the 1990 standard. ... The overwhelming fact is that no automobile manufacturer is on record stating that it would have added weight to its automobiles (or taken any other action) in any model year had the NHTSA relaxed the 1990 CAFE standard."

Actually, some government regulations have added to the weight of automobiles. "Since 1975, many new passenger-car and light-truck safety regulations have been implemented," the NRC noted in its July 2001 report. "It is estimated that these regulations added several hundred pounds to the average vehicle (e.g., air bags, improved impact protection). ... The CAFE regulations have not impeded the implementation of safety regulations and safety regulations have not prevented manufacturers from achieving their CAFE requirements."

In October 1999, the NHTSA calculated that airbags alone had saved 4,758 lives since their introduction while causing only 146 deaths, for a net savings of 4,612 lives. It seems rather hypocritical for CEI to oppose CAFE standards on safety grounds while simultaneously opposing airbags, but in fact CEI has gone so far as to suggest that Ralph Nader belongs in jail for endorsing them. At one point, CEI policy analyst Julie DeFalco even offered to publish directions for dismantling airbags on the CEI website.

And if CEI is truly concerned about saving lives, how do we explain its strident defense of the tobacco industry, in which one CEI commentator went so far as to suggest that smoking was a civic duty?

Related Resources

 * Competitive Enterprise Institute, "The Human Cost of Regulation:Reframing The Debate on Risk Management. A Proposal from the Competitive Enterprise Institute", 1994.
 * Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards, Committee on the Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards, Board on Energy and Environmental Systems, Transportation Research Board, National Research Council (Washington, DC: National Academies Press, 2001).
 * National Research Council, Automotive Fuel Economy: How Far Should We Go? (Washington, D.C.: National Academy Press, 1992),
 * Sam Kazman, ed., CEI's CAFE Litigation, January 29, 2002.