While most drivers believe that using a hands=free system to access their smartphone while driving is safer than directly using the device, a study (PDF) by the AAA Foundation for Traffic Safety found that hands-free systems, such as Apple’s Siri, still causes a high-level of mental distraction while behind the wheel.
Using a five-category rating system, researchers measured Siri-based interactions like sending and receiving text messages and emails, updating Facebook or Twitter, and modifying calendar appointments. Various measurements to record distraction were taken during three separate experiments, in-car on residential streets, without driving, and in a driving simulator.
Siri was tested on an iPhone 5, running iOS 7, and a microphone was used for voice commands in order to make the tests both hands-free and eyes-free, with drivers unable to look at or make contact with the device.
As shown in the chart above, Siri caused the highest distraction, and using Siri even resulted in two crashes in the simulator. Siri was given the lowest intuitiveness rating, while receiving the highest complexity rating. Researchers found Siri had a lack of consistency, and its voice command structure was inflexible.
The study also showed Siri would produce different responses to seemingly identical commands, requiring exact phrases to accomplish specific tasks, with any subtle deviations in phrasing resulting in failure.
Siri also proved inflexible when attempting to modify or edit a message or command, and also made mistakes such as calling the wrong contact from the device’s contact list.
Siri’s sarcasm and “wit” were also frustrating to some users.
The AAA study did not examine the use of CarPlay, Apple’s new in-dash system that allows users to access many features of their iPhone via voice commands to the vehicle’s infotainment system. Early reviews of CarPlay praise the systems integration with Siri, improving the experience when compared to using Siri directly on the device.
The study results come just ahead of a set of voluntary guidelines the AAA is working on in order to encourage drivers to cut back on the use of voice-based technologies when driving.