Toyota typically designs its floor mats with grommets that slip over hooks on the floor to prevent them from sliding. On the bottom side, the mats employ a rubber surface with "nibs" that create friction and further prevent them from moving. The company argues that when properly anchored, compatible floor mats are used, problems don't occur. "It's a challenge for engineers to imagine every way that people might misuse their product," said Michels of Toyota.
Two years ago, when Design News talked to experts about the Toyota situation, most were in agreement that the automaker's problems were unforeseeable. At the time, however, the company's engineers were considering multiple culprits, including the accelerator's friction lever, heater condensation, corrosion, electronics, and floor mats. Toyota has since examined the mats, shortened the pedals, lengthened the friction lever, added a spacer, and changed the linkage materials. NHTSA has also definitively announced that the electronics were not the problem.
Still, experts now say that the simple interactions between floor mat and pedal should have been easier to catch. "To be fair, there are only so many conditions that an engineer can think of," Eppinger said. "So while you can't fault them for not considering every circumstance, you can fault them for not considering enough."
An engineer's responsibility in such situations is essentially set by the legal system, experts said. "What it comes down to is that if you design something, you have to contemplate how people will misuse it," said David Cole, chairman emeritus of the Center for Automotive Research. "It's a fundamental area of law, but it's also a deterrent to innovation."
To be sure, vehicle manufacturers are complying with all measures designed to prevent future cases of unintended acceleration. In April, NHTSA proposed inclusion of a mandatory brake-throttle override system that would shut down the throttle if the brake and accelerator pedals are pressed simultaneously. Toyota already has the technology on its vehicles and the Alliance of Automobile Manufacturers has said they stand behind it, as well.
"The truth is, there's probably a very low risk that anything will happen," Champion said, referring to the floor mat problem. "It's one of those times when, yes, it could happen, so they're saying, 'Let's get the recall out anyway, just to be safe.'"