"It's no different from talking to a passenger"

If conversation is the problem, this belief says, then every car with two people in it is a hazard, and nobody's banning passengers. You talk to your partner on the motorway. You talk to your mate on the way to the football. A call is the same thing with the person somewhere else.

It isn't the same, and the difference is exactly where the person is. Frank Drews, Monisha Pasupathi and David Strayer had people drive a simulator while talking to a friend, either in the passenger seat or on a phone, about a time their life had been in danger, which is a conversation that takes some attention. Phone drivers made the most errors. And the recordings showed what passengers did that callers couldn't. The passengers talked about the traffic. Both driver and passenger simplified what they were saying when the road got harder. The conversation bent round the driving, because the passenger could see the driving.

Samuel Charlton went further. He compared passengers in the car, callers on hands-free, and a third group, callers who could see the driver's view through a window into the simulator. Passengers in the car slowed their talking as a hazard came up and sometimes said something about it. Callers did neither. The callers who could see the road did a little of it, and not enough to protect the driving. So it wasn't only about seeing. It was about being there, in the car, with your own body coming up to the roundabout too. Charlton also tried a phone that beeped at the caller when the driving got demanding, and that got the conversation close to what a passenger does. Nobody makes that phone.

The person on the phone doesn't know you're at a junction. They don't stop talking when the van pulls out. They keep going, because from where they are nothing's happening, and you keep up with them, because that's what a conversation is. A passenger is a second pair of eyes with a stake in the outcome. A caller is a voice that would like an answer. That's the whole difference, and it's a large one.

None of this makes passengers cost nothing, and a passenger who's upset or a child who's shouting takes attention too. But the belief that a call is just a passenger you can't see gets the difference backwards. The seeing is the point.