WASHINGTON, D.C. — A National Highway Traffic Safety Administration study, withheld from the public since 2003, found that hands-free mobile technology presents as much of a safety hazard as handheld phones.

The results were released earlier this week after two advocacy groups — Public Citizen and the Center for Auto Safety — obtained the data.

“By keeping this information secret from the public for the past six years, the government has endangered even more lives,” the groups stated. “Cities and States across the country have passed laws and ordinances requiring drivers to use hands-free phones, mistakenly believing those devices to be safe and encouraging drivers to use them.”

According to the study, it is the conversation itself, not the device used to hear it that causes “inattention blindness,” a cognitive state that slows a driver’s reaction time and limits his ability to detect changes in road conditions.

As well, the research and driving simulations analyzed in the NHTSA documents found that drivers using hands-free technology talk on the phone with greater frequency and for longer intervals.

“By withholding this data, the National Highway Traffic Safety Administration led consumers to believe that it was safe to talk on their cell phones while driving if they kept both hands on the wheel,” the groups said.

The Center for Auto Safety is petitioning NHTSA today to restrict the availability of two-way communication features through in-vehicle systems while the vehicle is in motion, relying in part on information revealed in the released records as a basis for the petition.

The Center also is asking NHTSA to support state programs designed to limit use of cell phones – whether hands-free or handheld – by drivers.