Safety Agency Widens Inquiry on Ford Floor Mats The National Highway Traffic Safety Administration has intensified an investigation into whether 480,000 Ford, Lincoln and Mercury vehicles have floors designed so that floor mats - if not properly secured - are nudged forward to snag the gas pedal and possibly cause unintended acceleration. In a report posted on the agency's Web site over the weekend, N.H.T.S.A. says its investigation covers 2008-10 Ford Fusions, Mercury Milans and Lincoln MKZ models. The agency says it is aware of 52 complaints from drivers who said floor mats prevented the accelerator pedal from returning to idle. But no accidents were reported. Consumers who complained to the agency often said the unintended acceleration typically occurred after the driver pushed hard on the accelerator, as when merging onto a highway. But when the driver eased off the gas, the engine speed didn't decrease. Drivers solved the problem by shifting into neutral or turning the engine off. It seems possible, the agency report said, that the design of the floor pan can lift an unsecured floor mat so that it reaches the gas pedal. The report noted mechanics who checked vehicles after owners complained of the problem blamed unsecured floor mats. Ford changed the design of the pedals early in the 2010 model year, government investigators found. And, the "elevated rates of pedal entrapment" were found in the 2008 -10 model years before that change was made. The agency began investigating the issue in May 2010 after receiving three complaints. In a letter to the agency dated Sept. 9, 2011, Ford's global director of its Automotive Safety office, Steven M. Kenner, wrote that problems with the gas pedal can occur only if the floor mat is not properly secured. It is not a serious issue because the driver can move the floor mat with a foot or by tapping the accelerator pedal, Mr. Kenner wrote. Consequently, he said, Ford does not see a safety defect or "unreasonable risk" to safety. More than two years is an unusually long time for the agency to go from a "preliminary evaluation" to the engineering analysis now under way. A N.H.T.S.A. spokeswoman could not immediately be reached for comment.