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Status Report, Vol. 42, No. 11 | December 22, 2007 Subscribe

Yes, improve fuel economy, but do it with safety in mind

Promoting fuel economy and enhancing safety are important goals that historically have been at odds, but they don't have to be.

Today's passenger vehicles are doing a much better job of protecting people in crashes, compared with predecessor models. Nearly every vehicle the Institute tests earns a top rating for frontal crashworthiness (see Status Report special issue: frontal crash test verifications, March 29, 2006), and automakers are quickly improving side ratings, too.

It will be important to keep these safety benefits in mind as Congress looks to toughen federal fuel economy standards. Otherwise, the new fuel economy requirements could compromise the safety of vehicles we drive in the future.

"Make no mistake — cutting fuel consumption is good conservation policy, good environmental policy, and in these times of rising energy prices it's also good economic policy," says Institute president Adrian Lund. "What Congress has to do is establish fuel consumption policies with safety in mind, making choices that raise fuel economy without compromising vehicle safety. Specifically, Congress has to change the way auto manufacturers comply with the federal fuel economy requirements."

Safety versus fuel conservation

Ever since corporate average fuel economy requirements were imposed in the 1970s, automakers have been complying by downsizing their vehicles so they use less fuel and/or by offsetting the fuel consumption of their bigger vehicles with sales of smaller, lighter, and more fuel-efficient ones. This approach of manipulating the size and weight of a vehicle mix to comply with federal requirements has been the quickest and easiest choice for automakers (see Status Report special issue: fuel economy and safety, Sept. 8, 1990) because of the direct link between a vehicle's weight and the fuel required to move it.

There's a cost in terms of safety. The smaller, lighter vehicles are at a disadvantage in collisions with larger vehicles. They're even at a safety disadvantage in many single-vehicle crashes. There's less structure outside the passenger compartment to crush and reduce crash forces on the occupants, so deaths and injuries are more likely to occur.

"We can't change this inherent disadvantage," Lund points out. "It goes to the laws of physics. The cars we drive today are designed to be safer than the models of previous years, but current cars still are smaller and lighter than they would have been if fuel economy standards hadn't been established 30 years ago. The effect on safety is well documented."

Study after study confirms that when vehicles are made smaller and lighter the risks go up. The National Academy of Sciences estimates that if the cars and light trucks that were on the road in 1993 returned to their average weight as of 1976, we could have saved about 2,000 lives in crashes during 1993 alone.

Existing fuel economy rules for cars ignore this trade-off between size and safety. The rules specify a corporate fuel average of 27.5 miles per gallon across each automaker's fleet, so the manufacturers offset sales of heavier, less efficient cars by increasing sales of lighter ones that use less fuel but also are less safe.

Rules for trucks factor in safety

The situation is different for SUVs, pickup trucks, and vans. A new federal standard for these passenger vehicles for the first time unlinks fuel economy improvements from their safety consequences (see "Proposed revision of fuel economy standards would be a win for safety," Feb. 25, 2006). All of these vehicles are required to become more fuel efficient, but bigger ones have to meet less stringent targets.

"Congress should allow the National Highway Traffic Safety Administration to set up a similar system for cars," Lund advises. "The key is that federal fuel economy targets shouldn't be applied uniformly across all sizes of passenger vehicles. That's contrary to physics, because it obviously takes more fuel to move more weight."

Applying the same fuel economy approach to cars that already governs SUVs, pickup trucks, and vans would mean all manufacturers wouldn't have to hit the same target. A fleet's fuel economy average would depend on the mix of vehicles consumers choose to buy. Then automobile fuel economy overall would improve, but automakers could achieve the improvement on a percentage basis by vehicle size.

"The safety implications are plain. Changing the way automakers comply would remove the long-standing incentive to meet fuel economy standards primarily by downsizing their cars, thus compromising crashworthiness," Lund says.

Under the improved method, downsizing would be discouraged because smaller vehicles would have to meet higher fuel economy requirements. Each decrease in car size could trigger an incremental increase in the fuel economy that's required. Instead of downsizing their vehicles, the manufacturers would be forced use engine technologies to meet the fuel-saving targets established by the federal government.

"This is something automakers have resisted in the past," Lund adds. "They've preferred to use innovative engine technologies to enhance the performance of their vehicles, not conserve fuel. Congress could take a couple of steps to put an end to this."

Vehicle horsepower, travel speeds

One step would be for Congress to cap vehicle horsepower. Ten years ago only a handful of exotic and/or expensive luxury cars were capable of 300 horsepower. Now many everyday cars from Chryslers to Subarus match this. Today's average horsepower of 195 is 87 percent higher than it was in 1983, surpassing even the average during the muscle car era of the 1960-70s.

Something else Congress could do is lower the speed limits. Deaths in crashes declined when states enacted 55 mile per hour speed limits in the early 1970s. Since then, numerous studies have found increases from 15 to 30 percent in deaths on roads where speed limits were raised from 55 mph after the national maximum speed limit was repealed.

Speeding is a factor in 30 percent of all fatal crashes, killing more than 1,000 Americans every month, according to federal estimates. Yet speed limits continue going up. Texas recently raised the limit on some highways to 80. To put this in perspective, frontal crash tests typically are conducted at 35 to 40 miles per hour, speeds that produce severe impacts.

"I don't know if there's political will to lower speed limits, but there certainly isn't any reason not to apply the same kind of fuel economy standards to cars as to trucks," Lund concludes. "This would help with the horsepower escalation rate as automakers would be forced to use some engine technology innovations to reduce their vehicles' fuel consumption."

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