Effect of Fuel Economy on Automobile Safety: A Reexamination

Abstract

Since 1975, the fuel economy of passenger cars and light trucks has been regulated by the corporate average fuel economy (CAFE) standards, established during the energy crises of the 1970s. Calls to increase fuel economy are usually met by a fierce debate on the effectiveness of the CAFE standards and their impact on highway safety. A seminal study of the link between CAFE and traffic fatalities was published by R. W. Crandall and J. D. Graham in 1989. They linked higher fuel economy levels to decreases in vehicle weight and correlated the decline in new car weight with about a 20% increase in occupant fatalities. The time series available to them, 1947-1981, includes only the first 4 years of fuel economy regulation, but any statistical relationship estimated over such a short period is questionable. This paper reexamines the relationship between U.S. light-duty vehicle fuel economy and highway fatalities from 1966 to 2002. Cointegration analysis reveals that the stationary linear relationships between the average fuel economy of passenger cars and light trucks and highway fatalities are negative: higher miles per gallon is significantly correlated with fewer fatalities. Log-log models are not stable and tend to produce statistically insignificant (negative) relationships between fuel economy and traffic fatalities. These results do not definitively establish a negative relationship between light-duty vehicle fuel economy and highway fatalities; instead they demonstrate that national aggregate statistics cannot support the assertion that increased fuel economy has led to increased traffic fatalities.

Examining fuel economy and carbon standards for light vehicles

“…There are widely differing estimates of oil use externalities (NRC, 2002;Lutter and Kravitz, 2003) and the safety impacts of reducing size and weight (Kahane, 2003;Van Auken and Zellner, 2003;Ross and Wenzel, 2002;Ahmad and Greene, 2005), so it is difficult to weigh these arguments. However, there is ample evidence that vehicle purchasers do not behave as ''rational consumers,'' at least in terms of how economists define such consumers.…”

Accident Cost, Speed and Vehicle Mass Externalities, and Insurance

“…Crandall and Grahams study from 1989 using aggregate data claim that the Corporate Average Fuel Economy (CAFE) program that requires a minimum fuel efficiency standard has led to lighter vehicles and thereby additional fatalities. Several studies have questioned Crandall and Grahams result (Ahmad and Greene, 2005) and especially emphasized that a replacement of cars by light trucks like SUVs has lead to more fatal accidents (White, 2004). Our model gives no support either to downsizing the vehicle fleet or upsizing it but suggests that it is the mass difference that should be reduced.…”

Triple Safety: Lightweighting Automobiles to Improve Occupant, Highway, and Global Safety

“…Kazzhoum (1994) critiqued Crandall and Graham and reran their analysis using data from 1985 to 1989, which generated the result that increased car weight caused the number of fatalities in single-car crashes to go up. Ahmad and Greene (2004) reexamined Crandall and Grahamʼs studies using data from 1966 to 2002, and found that the statistics could not support the assertion that increased fuel economy has led to a greater number of traffic fatalities.…”