The autonomous car has a big problem: nobody can agree what it is. The argument was brought into relief earlier this year when Elon Musk casually remarked that a Tesla would drive itself across the US within 24 to 36 months.

It was a great bit of scene-stealing. Tesla wasn’t at the Geneva show, but Musk's prediction ensured that pretty much every senior executive in attendance was being asked about self-driving cars.

The big argument is at what level does a car become truly autonomous? Is it when the car is able to pilot itself some of the time, or when it is capable of operating without any human intervention? Nissan CEO Carlos Ghosn, keen to defend what he says is his company’s leading position on self-driving cars, was openly critical of Musk’s announcement.

“If it’s a question of being autonomous on one lane of a highway or maybe changing lanes, then this is 2016 or 2017,” he said. “But if you’re talking about autonomous driving in a city with crossroads, or the car making decisions in complicated situations, then frankly I don’t think it’s going to be ready before 2020.”

That date neatly coincides with Nissan’s previous prediction on when it will release its first self-driving cars. His position was echoed by Volkswagen executives, with Scott Keogh, President of Audi of America, telling journalists the company reckons click-and-go autonomy is even further away.