A renowned university professor has some expert manufacturing insight for potential buyers of hybrid or plug-in vehicles.

“The bottom line is: before you buy, consider how you drive,” says Jeremy Michalek, a professor of engineering, mechanical engineering, and public policy at Carnegie Mellon University, in Pittsburgh.
His new study – funded by the National Science Foundation, Ford, and Toyota, and which will appear in the journal Energy Policy – reveals new information about fuel economy standards regarding hybrids and plug-in vehicles.

Working with mechanical engineering research assistant, Orkun Karabasogiua, Michalek analyzed the potential cost and greenhouse gas savings of hybrids and plug-ins under various driving conditions.

Michalek says their research finds that “for highway drivers, hybrid and plug-in vehicles cost more without much benefit to the environment.”

However, for those who drive in a lot of stop-and-go traffic, like city drivers, hybrids and plug-ins have the most value and “could lower lifetime costs by 20 percent and cut greenhouse gas emissions in half.”

For traffic drivers, he says, this situation is a “win-win,” adding that the “benefits may be much more than the labels suggest.”

The study was prompted by the US Environmental Protection Agency’s announcement that they would start using new fuel economy labels, beginning with 2013 vehicles.

The American government regularly uses standard laboratory tests to measure vehicle fuel efficiency for federal fuel economy labels and standards.

“The fuel economy standards are still based on old lab tests that make vehicles appear to be more efficient than they really are,” Michalek says. “This has always been an issue, but it is simplified with today’s vehicle technologies. These tests may be underestimating the relative real-world benefits of hybrid and plug-in vehicles.”

And driving conditions affect more than just cost and emissions, Michalek explains.

“Aggressive driving can cut vehicle range by 40 percent or more. That’s a notable risk for pure electric vehicles, which already have limited range and take a long time to recharge,” he says. “But with hybrid electric vehicles, which run on gasoline, and plug-in hybrid electric vehicles that use electricity for short trips and switch to gasoline for longer trips, there’s no added risk of being stranded.”

About Carnegie Mellon University
Carnegie Mellon is a private, internationally ranked research university with programs in areas ranging from science, technology, and business, to public policy, the humanities and the arts. More than 12,000 students in the university’s seven schools and colleges benefit from a small student-to-faculty ratio and an education characterized by its focus on creating and implementing solutions for real problems, interdisciplinary collaboration and innovation.


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