"These parts are made collapse to absorb shock so they'll sustain more damage," O'Dell says. In older models, "you absorb the shock—that's the big difference," he adds.
While automakers have unveiled a slew of lighter, sleeker vehicles in Detroit this week, that doesn't mean hybrid and electric vehicles are out of fashion.
Carmakers understand that "they have to do both," Belzowski says. "You can't just do one or the other."