Myth: Reducing Greenhouse Gas Emissions Will Also Reduce Auto Safety.
Issue
To fight global warming, California adopted regulations limiting greenhouse gas emissions from cars, SUVs and pick-up trucks. The auto industry has sued in various forums to stop those regulations. When those lawsuits have not succeeded, the auto industry has tried to convince Congress and the Bush Administration to block California’s global warming efforts.
Myth
The auto industry claims that reducing greenhouse gas emissions will reduce auto safety for three reasons:
- In order to meet the greenhouse gas emissions regulations, auto manufacturers must produce a fleet of smaller, lighter cars that are less crashworthy and will result in more highway fatalities and injuries.
- Vehicles that meet the greenhouse gas emission regulations will get better mileage per gallon so people will drive more simply because the cost is cheaper. More vehicle miles traveled will lead to more accidents and injuries.
- Vehicles that meet the greenhouse gas emission regulations will be more expensive. People will wait to buy new cars, and the fleet of cars on the road will be older and not have the safety improvements added to newer vehicles.
Truth
There is no evidence that the greenhouse gas regulations will lead to lighter cars-- either decreases in the weight of the vehicle fleet of any manufacturer or of the combined fleet of all auto manufacturers. A federal court judge in Vermont who heard exhaustive testimony about the auto manufacturers’ safety arguments in opposition to California’s regulations noted that the manufacturers “did not offer expert testimony suggesting that the regulation will lead to smaller vehicles or that smaller vehicles are less safe.” Ultimately, the judge concluded that “it appears clear that any negative safety impact arising from the regulation will result from changes in consumer behavior, not from any flaw in technology or design likely to be used to reduce GHG [greenhouse gas] emissions.” Green Mountain Chrysler et al v. Crombie U.S. District Court Vermont, No. 2:05-cv-00302-wks, Sept. 12, 2007 opinion at p. 219 and p. 221 See decision.
While the laws of physics suggest that a lighter vehicle will come out worse in a collision with a heavier vehicle, the greenhouse gas regulations are aimed at fleet-wide averages and not at specific vehicles. The same laws also predict that there will be no effect if the mass of both vehicles is reduced proportionately. If all vehicles’ weight were reduced by 10%, there would be no effect on safety. Thus, the key premise of the argument that fuel economy improvements leads to reduced safety doesn’t work when there is a fleet-wide reduction in vehicle weight.
Empirical evidence shows that there is no causal link between fuel economy and traffic fatalities and injuries. Historically, improvements in fuel economy have not led to a smaller, less crashworthy fleet. On the contrary, the average fuel economy of passenger cars and light trucks sold in 2005 was 60% greater than that of passenger cars and light trucks sold in 1975, despite the fact that the average weight of passenger cars and light trucks sold in 2005 was actually 29 pounds greater than the average weight of passenger cars and light trucks sold in 1975. 1
The auto manufacturers’ alternate safety theories are speculative and logically inconsistent. For example, accepting the assertion that the new, more fuel efficient vehicles will have a higher purchase price, the lower cost of operating those vehicles will not necessarily lead to more vehicle miles traveled because the consumers who purchase those vehicles will have less money left over to buy fuel. The Vermont court heard all of the auto manufacturers’ evidence on these matters and concluded that their predictions were riddled with uncertainties and were unreliable. The Court also found that any potential decrease in safety would be outweighed by increases in safety taking place over time. Green Mountain Chrysler, Sept. 12, 2007 opinion at pp. 216-22. See decision.
The bottom line: Greenhouse gas emissions regulations will not reduce safety on the highway.
- Auto manufacturers often point to a 2002 study by the National Academy of Sciences which suggested that there may have been a correlation between fuel economy and highway safety in the 1980s. However, since that report was released, important scientific studies and peer-reviewed journal articles have been published that refute the supposed link between fuel economy and traffic safety, including Ahmad, S. & D.L. Greene, “Effect of Fuel Economy on Automobile Safety: A Reexamination,” Transportation Research Record 1941, Transportation Research Board of the National Academies, (2005); and Van Auken, R.M. & J.W. Zellner, “A Review of the Results in the 1997 Kahane, 2002 DRI, 2003 DRI and 2003 Kahane Reports on the Effects of Passenger Car and Light Truck Weight and Size on Fatality Risk,” DRI-04-02, Dynamic Research, Inc., Torrance, California (2004).