Despite its good intentions, using Siri while driving is actually quite dangerous, according to a new study from the AAA Foundation for Traffic Safety. After a series of tests involving 45 drivers completing in-car tasks with various voice control systems, researchers found Apple’s digital assistant to be a “high level of mental distraction.”

In fact, Siri performed the worst out of all of the various systems they tested, and even resulted in two crashes during the simulator study. The popular assistant was also rated the least intuitive and the most complex, and AAA criticized it for its lack of consistency and flexibility when it came to recognizing voice commands from its drivers.

The drivers were monitored for a variety of feedback cues including heart rate, brain functions and peripheral vision detection and response. And these things were tracked as the drivers performed the variety of voice command tasks in three separate environments: not driving, driving in a simulator, and driving in residential streets.

It’s worth noting here that researchers looked at Siri in iOS version 7.0, not iOS 8 where the feature has been [arguably] much improved, and more importantly neglected CarPlay. They also graded Siri on sending/receiving messages, updating Twitter and managing Calendars—tasks far more complex than the others were capable of.

As for OEM offerings, Toyota’s Entune was found to be the least distracting with a ranking of 1.7. Hyundai’s Blue Link came in at 2.2, Chrysler’s Uconnect at 2.7, and Ford’s SYNC with Touch was rated a 3.0. Chevrolet’s MyLink was the worst out of the automotive industry, with a distraction level at 3.7, though it still beat out Siri at 4.0.

AAA’s study arrives as the first aftermarket CarPlay head units have become available. Apple announced the project last summer, but we have yet to see it roll out to many production vehicles (outside of Ferrari). In its hands-on review of CarPlay, Consumer Reports found the system to be intuitive and effective at reducing distraction.

[AAA Newsroom]