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Crash Test Dummies

Challenging the safety myth
By Cam Burns

It was summer 2000, and Laura Schewel was driving to her internship position in Richmond, Virgina. As she passed through a notoriously dangerous intersection, a Class-D truck barreled into the side of her ’98 Honda Accord.

Luckily, she walked away from the crash. A full year later, after many hours of physical therapy, Schewel’s back injury had fully healed, but getting behind the wheel again remained a nerve-wracking ordeal.

Thankfully, time heals on many levels and Schewel’s experience on that early August morning cultivated a professional interest in automotive safety and design. Back then there was no way to imagine that only eight years later she’d be crashing two vehicles together hundreds and hundreds of times—albeit virtually—just to see what would happen to the people inside.

When Schewel joined RMI in 2006, her first assignment was to update "Winning the Oil Endgame," RMI’s 2004 roadmap for getting the United States off oil. But when she had the chance to lead a project aimed at making vehicles as safe as they can possibly be, she jumped at it.

Simply put, she was asked to look into the notion that lightweight vehicles can be just as safe as regular vehicles. By studying the dummies and vehicles that she repeatedly crashes in computer simulations, and examining the physics behind those collisions, Laura now has the opportunity to fully understand the forces she previously experienced firsthand.

“There’s a lot of compelling anecdotal evidence that light cars can be as safe as regular cars,” she says, “but there was no academic or statistical base. As I catalogued the studies that had been done, I realized there was a really significant gap in the literature.”

The “gap” she mentions was simply the fact that while there were studies that described what might happen to people in a car that was a few pounds lighter, there was nothing describing what would happen with a car that had gone on a real diet—and lost, say, 40 to 50 percent of its mass.

“In every major study there’d be this little footnote that said while lighter is not necessarily more dangerous, we don’t want to be held to that statement up to more than 100–200 pounds,” she says. “Those little footnotes were a problem for us.”

So, Laura wrote up “a little paper” about the many ways vehicles can be safer for the planet and for both drivers and other road users and presented it at a Society of Automotive Engineers conference where it was well received. With that success, she subsequently wrote a blog post for Yahoo! Green about the subject.

Yahoo!’s editors liked the piece so much they moved it to their homepage, where it was viewed more than 300,000 times.

“All of a sudden the site traffic for rmi.org went crazy, and people were sending me death threats via outreach,” she recalls. “I thought, wow, this is really a hot topic. We should pay a bit more attention to it.”
About the same time—as luck would have it—Schewel had crafted a proposal centered on exploring the literature gap. A flurry of emails went around RMI, the proposal was submitted and, just a week later, the William and Flora Hewlett Foundation committed to fund the project.

Today, RMI’s MOVE Team is deep into researching whether lightweight cars can be just as safe as heavy cars.

Model Dummies

The research involves creating computer models to simulate crashes of lightweight vehicles and popular on-the-road vehicles of about the same size. MOVE Team Analyst Mike Simpson is in charge of the modeling and is working with a subcontractor who will generate 500 virtual crashes in real-world configurations.

Most people, says Simpson, assume that in a collision a heavier car will fare better than a lighter one.

“The computer models are based on Newton’s Laws but you don’t have a solid single particle the way most people expect,” he says. “You actually have multiple components that all react differently depending on their orientation, the material they’re made of, their mass, the components around them they react with, and other considerations. And there are so many different materials in a car that it becomes a pretty complicated problem pretty quickly.”

Specifically, the computer doing the modeling divides the cars into tiny tetrahedrons (pyramid-shaped particles) that represent parts of the car. Millions of the tetrahedrons might represent the bumper, for example. Tens of thousands might make up a door handle. The tetrahedrons are then assigned values for various characteristics of that component (density, material characteristics, deformation properties, etc.).
“The bumper, for instance, is a single piece of metal or plastic,” Simpson explains. “But you don’t analyze it as a single solid piece of plastic or metal.”

The computer will then pull together what happens to the millions of tetrahedrons and generate images and animations of how the vehicle deforms, where the forces are greatest, and, ultimately, what happens to the people inside.

The larger the number of particles studied, the clearer the picture becomes of what happens—“higher resolution,” Simpson calls it.

Once the testing is complete, MOVE researchers will write a technical paper on their findings and publish it on a dedicated Web site. In addition to this crash testing, Schewel will design a market survey to query vehicle buyers on their attitude toward light vehicles.

The Target Audience

The MOVE Team has several specific audiences targeted for this research. First are vehicle buyers themselves, who, according to MOVE Team research thus far, are overwhelmingly women in their 20s, 30s, and 40s.

The second audience—perhaps the most important one—consists of insurance providers. Some members of the insurance industry associate lightweight cars with danger. That’s because they’re accustomed to steel cars. And steel cars that are lighter have, by definition, less steel in them, which makes them more dangerous.

Anything that’s new to insurance companies is going to be an inherent risk,” says Simpson. “That’s just how insurance companies operate. And insurance companies know steel vehicles because that’s all we have.”

Besides the obvious greenhouse-gas emissions and fuel savings-related benefits of lightweight cars, Schewel is quick to point out that there are huge benefits to the people who might be hit by lightweight cars: pedestrians, cyclists, and drivers of other vehicles. That means that the government will become another key audience.

“All the indications are that the benefits to other road users are going to outweigh benefits to the car drivers themselves,” she notes. “And it is absolutely in the insurance industry and government’s interest to promote those societal benefits. In Europe they’re really focused on pedestrian safety and ‘other-car’ safety but that wave of regulations hasn’t hit the U.S. as hard yet.”

One of the big challenges with lightweighting cars will be aligning individual consumer interest with societal goals. There are ways to do that, Schewel says, but for now, she’s just glad that the effects of lightweighting on carbon emissions and safety look extremely positive.

“Car crashes are the second-leading cause of death among young people between five and 29 years old, worldwide,” Schewel adds. “So it’s an extraordinary example of multiple solutions for a single expenditure, if you can simultaneously bring down these two scourges on society: global warming and traffic deaths.”

Cam Burns is RMI's Senior Editor

--Published Fall/Winter 2008
 

 
 
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