Expert Commentary

Fuel-efficient cars may actually be safer than gas guzzlers

Critics of fuel-efficiency standards have long argued that, by making cars lighter, they make cars more dangerous. A new paper challenges this theory, arguing that they may be saving lives.


When the United States started demanding that cars swig less fuel, critics argued that the efficiency standards, because they lower the cars’ weight, would make them more vulnerable in an accident. But a new paper challenges that theory, arguing that efficiency standards are likely saving lives.

What matters is not only the average weight of the car, as researchers have argued in the past. Instead, Antonio Bento of the University of Southern California and his colleagues write for the National Bureau of Economic Research, researchers should study how the weight is distributed across a carmaker’s fleet after those cars are redesigned to meet the new standards.

The debate has taken on urgency since Donald Trump’s inauguration. The president has pledged to review fuel-efficiency standards – known as Corporate Average Fuel Economy (CAFE) – and has hinted he will ease them. Meanwhile, car accidents remain the leading cause of death for American teenagers.

Bento and his colleagues examine data on cars sold in the U.S. between 1954 and 2005, determining that fuel-efficiency regulations lower the average vehicle weight and increase the way weight is dispersed across all the vehicles in a carmaker’s lineup. (In this dispersion, some cars become lighter relative to the average and some, such as SUVs, heavier.) For every 40 to 50 pounds of weight a car loses, it gains about 1 mile per gallon (MPG) in efficiency.

The team then looks at 17 million accident reports between 1989 and 2005, controlling for improvements in safety technology. It finds the increased dispersion associated with a higher chance of a fatality (if you take two random cars from the lineup and crash them, the probability of a fatality increases). But the team finds the lower average weight associated with a reduction in fatalities – both when the car is involved in an accident by itself or when the crash involves multiple vehicles.

Taking these two changes together, the authors estimate there are between 393 and 439 fewer vehicle fatalities in the United States annually.

Bento and his colleagues are economists, so they monetize the gains. The Department of Transportation values a human life at $9.4 million (macabre, yes, but run with this thought experiment). Totaling lives saved, they estimate the “welfare benefits” – a concept economists use to compare policies – of fuel standards at well over $3.5 billion annually (393 lives saved x $9.4 million = $3.7 billion). Compare that with the cost to the car industry of complying with emissions standards, which the Environmental Protection Agency estimated was around $1.5 billion in 2011. So even if the standards cost carmakers more, the authors declare they “would pass a cost-benefit test based on benefits from reduced fatalities alone.”

Other research:

A 1989 paper in the Journal of Law and Economics determined that CAFE standards were associated with a 500-pound reduction in average vehicle weight and that this lighter vehicle, in an accident, was associated with a 27 percent higher chance of a fatality.

A 2013 paper in the American Economic Journal: Applied Economics found a similar effect. For every 1 MPG increase in fuel-efficiency, wrote Mark Jacobsen of the University of California at San Diego, 149 more people die each year on America’s roads. “In other words, the increase in fuel-efficiency requirements that began in 1978 will translate into 2,533 more deaths on the road in 2016,” Jacobsen wrote. The same year, he published a paper in the American Economic Journal: Economic Policy that found the costs of efficiency standards fall disproportionately on lower-income households.

A 2011 paper for the National Bureau of Economic Research found that drivers involved in a collision with a car heavier than their own are more likely to die.

The conservative Heritage Foundation has argued against fuel-efficiency standards, reasoning that efficient cars are more deadly. Libertarians, too, have rallied against them, arguing that they do not save fuel or reduce carbon dioxide emissions.

According to the Centers for Disease Control and Prevention, 33,736 Americans died in car accidents in 2014; vehicle accidents were the leading cause of death for teenagers.

The U.S. introduced fuel-efficiency standards after the 1973 Arab oil embargo. We have a tip sheet on how oil impacts almost every journalistic beat.