Voice controls are touted as the "safe" alternative to fumbling with our phones, and yes, they keep our eyes on the road and our hands on the wheel. But the technology is still half-baked, and in the case of Apple's Siri, it's distracting enough to cause two crashes in a simulator.

A study from AAA proves, once again, what we already suspected: voice-activated functionality is distracting because it's both prone to errors and increases cognitive load. And Siri is one of the worst offenders.

The AAA rated distraction on scale of 1 to 4, with one being equivalent to listening to the radio and 3 listening to and composing text-related messaging.

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Toyota's Entune system led the pack with a score of 1.7, although its functionality is limited compared to other systems. Hyundai's BlueLink scored the second slot with a 2.2, followed by Chrysler's Uconnect (2.7), MyFord Touch (3.0), Mercedes' Comand (3.1), and Chevy's MyLink (3.7). But Siri knocked it out of the par, scoring a 4.15.

From the report (PDF), emphasis mine:

The participant neither looked at nor made physical contact with the iPhone during these interactions. Even so, the workload ratings exceeded category 4 on our workload scale – the highest ratings that we have observed for any task short of OSPAN. Moreover, there were two crashes in the simulator study when participants used Siri (the only other crash we observed was when participants used the menu-based systems).

Siri had the lowest level of intuitiveness and the highest level of complexity, which caused a series of mistakes, including calling the wrong person. And some of the people in the test "reported frustration with Siri's occasional sarcasm and wit," because nobody wants a smart-ass AI when you're trying to get stuff done.

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The AAA admits that it didn't test Google Now or Microsoft's new Cortana systems, both of which could have a slight edge on Siri.

But the larger point of the study isn't that these systems fail and we should revert back to texting with our thumbs and holding our phones to our ears – we just need to focus on the road.

"The primary task should be driving," says David Strayer, the study leader and a psychology professor at the University of Utah. "Things that take your attention away make you a poor driver. Even though your car may be configured to support social media, texting and phone calls, it doesn't mean it is safe to do so."