Just because you can use a voice-activated system or app in your car doesn’t mean you should.

Such is the warning from the AAA Foundation for Traffic Safety, which says the hands-free systems—common in many new cars—tend to take your attention away from the road, which is a problem for people who are trying to, y’know, drive.

The foundation, with the help of the University of Utah and Precision Driving Research, tested a number of voice-activated vehicle systems and found that, depending on the feature being used and the accuracy of the system, the devices had a high potential to distract the driver.

It is clear that not all voice systems are created equal, and today’s imperfect systems can lead to driver distraction.

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

The tests revealed that some in-vehicle technologies are better than others. For example, Toyota’s Entune system scored a 1.7 on AAA’s 5-point cognitive distraction scale—comparable to listening to an audiobook. Systems by Chevrolet, Ford, and Mercedes scored 3 points or higher on the distraction scale, while Hyundai’s and Chrysler’s systems did slightly better.

And apps can be worse: The iOS 7 version of Apple’s Siri scored a whopping 4 out of 5 on the mental-distraction scale.

The 5-point scale came from the University of Utah, which created the test during a 2013 study on distracted driving. Precision Driving Research led the testing, which was intended to encourage a higher quality of devices in the future—something that AAA, despite its mixed take on the technology, said is possible.

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

Curious about the full results? Check out the study over this way [PDF].

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