Siri may not be the hands-free savior Apple intended her to be. A new study by the AAA Foundation for Traffic Safety ranks iOS 7 Siri as one of drivers’ worst distractions.

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AAA noted that even though three out of four drivers think hands-free technology is safe to use on the road, it can be deceptively distracting, with potentially dangerous results.

“Technologies used in the car that rely on voice communications may have unintended consequences that adversely affect road safety,” AAA Foundation for Traffic Safety’s president and CEO Peter Kissinger said in a statement. “The level of distraction and the impact on safety can vary tremendously based on the task or the system the driver is using.”

The study measured drivers’ reaction time with equipment such as instrumented test vehicles and heart-rate monitors. Although Siri is hands-free and eyes-free, drivers using the Apple function to perform a number of tasks experienced some of the most elevated levels of distraction.

“It is clear that not all voice systems are created equal, and today’s imperfect systems can lead to driver distraction,” said AAA CEO Bob Darbelnet. “AAA is confident that it will be possible to make safer systems in the future.”