It takes 27 seconds to regain focus after talking to Siri

Or other in-car hands-free systems

For years, hands-free systems have been touted as a safer way to operate your mobile phone while you drive. But a team of psychologists has found that smartphone personal assistants and in-car information systems are pretty distracting in their own right.

Researchers at the University of Utah tested Microsoft Cortana, Apple Siri and Google Now, asking 65 people to use them to dial phone numbers, call contacts, change music and send texts. They also examined a selection of voice-dialing, voice-contact calling and music selection systems in ten cars released in 2015, tested by 257 people.

The found that a driver travelling 25 mph continues to be distracted for up to 27 seconds after disconnecting from most phone and car voice-command systems. That's a distance of three American football fields.

Study results

'Impaired Attention'

"Most people think, 'I hang up and I'm good to go,'" said David Strayer, senior author of the two new studies. "But that's just not the case. We see it takes a surprisingly long time to come back to full attention. Even sending a short text message can cause almost another 30 seconds of impaired attention."

They also found that experience using voice-recognition systems doesn't eliminate distraction, and that older drivers are much more distracted than younger drivers when giving voice commands.

"Just because these systems are in the car doesn't mean it's a good idea to use them while you are driving," said Strayer. "They are very distracting, very error prone and very frustrating to use. Far too many people are dying because of distraction on the roadway, and putting another source of distraction at the fingertips of drivers is not a good idea. It's better not to use them when you are driving."

You can find the full studies, with full details, on the American Automobile Association's website.